Search Results

Search found 50723 results on 2029 pages for 'class loading'.

Page 3/2029 | < Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >

  • Using a class within a class?

    - by Josh
    I built myself a MySQL class which I use in all my projects. I'm about to start a project that is heavily based on user accounts and I plan on building my own class for this aswell. The thing is, a lot of the methods in the user class will be MySQL queries and methods from the MySQL class. For example, I have a method in my user class to update someone's password: class user() { function updatePassword($usrName, $newPass) { $con = mysql_connect('db_host', 'db_user', 'db_pass'); $sql = "UPDATE users SET password = '$newPass' WHERE username = '$userName'"; $res = mysql_query($sql, $con); if($res) return true; mysql_close($con); } } (I kind of rushed this so excuse any syntax errors :) ) As you can see that would use MySQL to update a users password, but without using my MySQL class, is this correct? I see no way in which I can use my MySQL class within my users class without it seeming dirty. Do I just use it the normal way like $DB = new DB();? That would mean including my mysql.class.php somewhere too... I'm quite confused about this, so any help would be appreciated, thanks.

    Read the article

  • Identifying that a variable is a new-style class in Python?

    - by Dave Johansen
    I'm using Python 2.x and I'm wondering if there's a way to tell if a variable is a new-style class? I know that if it's an old-style class that I can do the following to find out. import types class oldclass: pass def test(): o = oldclass() if type(o) is types.InstanceType: print 'Is old-style' else: print 'Is NOT old-style' But I haven't been able to find anything that works for new-style classes. I found this question, but the proposed solutions don't seem to work as expected, because simple values as are identified as classes. import inspect def newclass(object): pass def test(): n = newclass() if inspect.isclass(n): print 'Is class' else: print 'Is NOT class' if inspect.isclass(type(n)): print 'Is class' else: print 'Is NOT class' if inspect.isclass(type(1)): print 'Is class' else: print 'Is NOT class' if isinstance(n, object): print 'Is class' else: print 'Is NOT class' if isinstance(1, object): print 'Is class' else: print 'Is NOT class' So is there anyway to do something like this? Or is everything in Python just a class and there's no way to get around that?

    Read the article

  • How to get a Class literal from a generically specific Class

    - by h2g2java
    There are methods like these which require Class literals as argument. Collection<EmpInfo> emps = SomeSqlUtil.select( EmpInfo.class, "select * from emps"); or GWT.create(Razmataz.class); The problem presents itself when I need to supply generic specific classes like EmpInfo<String> Razmataz<Integer> The following would be wrong syntax Collection<EmpInfo<String>> emps = SomeSqlUtil.select( EmpInfo<String>.class, "select * from emps"); or GWT.create(Razmataz<Integer>.class); Because you cannot do syntax like Razmataz<Integer>.class So, how would I be able to squeeze a class literal out of EmpInfo<String> Razmataz<Integer> so that I could feed them as arguments to methods requiring Class literals? Further info Okay, I confess that I am asking this primarily for GWT. I have a pair of GWT RPC interface Razmataz. (FYI, GWT RPC interface has to be defined in server-client pairs). I plan to use the same interface pair for communicating whether it be String, Integer, Boolean, etc. GWT.create(Razmataz) for Razmataz<T> complains that, since I did not specify T, GWT compiler treated it as Object. Then GWT compiler would not accept Object class. It needs to be more specific than being an Object. So, it seems there is no way for me to tell GWT.create what T is because a Class literal is a runtime concept while generics is a compile time concept, Right?

    Read the article

  • Getting the class of an n dimensional array of an runtime supplied class name

    - by MeBigFatGuy
    Given a fully qualified class name, and a number of dimensions, i would like to get the Class name for this class. I believe i can do this like such public Class<?> getArrayClass(String className, int dimensions) throws ClassNotFoundException { Class<?> elementType = Class.forName(className); return Array.newInstance(elementType, new int[dimensions]).getClass(); } However this requires me to create an unneeded instance of the class. Is there a way to do this without creating the instance? It does not appear that Class.forName("[[[[Ljava/lang/String;") (or a algorithmically generated version) works correctly in all instances from various blog posts i've seen.

    Read the article

  • Returning and instance of a Class given its .class (MyClass.class)

    - by jax
    I have an enum that will hold my algorithms. I cannot instantiate these classes because I need the application context which is only available once the application has started. I want to load the class at runtime when I choose by calling getAlgorithm(Context cnx). How do I easily instantiate a class at runtime given its .class (and my constructor takes arguments)? All my classes are subclasses of Algorithm. public enum AlgorithmTypes { ALL_FROM_9_AND_LAST_FROM_10_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), ALL_FROM_9_AND_LAST_FROM_10_CURRENCY_ID(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), DIVIDE_BY_9_LESS_THAN_100(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class), TABLES_BEYOND_5_BY_5(AlgorithmFactory.AlgorithmAllFrom9AndLastFrom10Impl.class); private Class<? extends Algorithm> algorithm; AlgorithmTypes(Class<? extends Algorithm> c) { algorithm = c; } public Algorithm getAlgorithm(Context cnx) { return //needs to return the current algoriths constructor which takes the Context Algorithm(Context cnx); } }

    Read the article

  • How to add class to selective <li> in a generated menu

    - by Vikram
    Hi I am looking for a solution to add a class to every list item <li> which has a child item with a class of <span class="separator"> and a different class to <li> with an anchor link. I use Joomla and the menu is being generated somewhat like this: <ul class="menu"> <li class="item1"><a href="<!-- link goes here -->"><span>Home</span></a></li> <li class="parent item59"><span class="separator"><span>Demo</span></span></li> <li class="item62"><a href="<!-- link goes here -->"><span>Article</span></a></li> <li id="current" class="parent active item27"><a href="<!-- link goes here -->"><span>CMS</span></a> <ul> <li class="item50"><a href="<!-- link goes here -->"><span>The News</span></a></li> <li class="item48"><a href="<!-- link goes here -->"><span>Web Links</span></a></li> <li class="item65"><span class="separator"><span /></span></li> <li class="item49"><a href="<!-- link goes here -->"><span>News Feeds</span></a></li> <li class="item66"><span class="separator"><span /></span></li> <li class="item67"><span class="separator"><span /></span></li> <li class="item68"><span class="separator"><span /></span></li> </ul> </li> <li class="item71"><span class="separator"><span>Help</span></span></li> </ul> What I want is to add class "anclink" or "seplink" to the <li> depending on their child item so that the final output looks like below. <ul class="menu"> <li class="item1 anclink"><a href="<!-- link goes here -->"><span>Home</span></a></li> <li class="parent item59 seplink"><span class="separator"><span>Demo</span></span></li> <li class="item62 anclink"><a href="<!-- link goes here -->"><span>Article</span></a></li> <li id="current" class="parent active item27" anclink><a href="<!-- link goes here -->"><span>CMS</span></a> <ul> <li class="item50 anclink"><a href="<!-- link goes here -->"><span>The News</span></a></li> <li class="item48 anclink"><a href="<!-- link goes here -->"><span>Web Links</span></a></li> <li class="item65 seplink"><span class="separator"><span /></span></li> <li class="item49 anclink"><a href="<!-- link goes here -->"><span>News Feeds</span></a></li> <li class="item66 seplink"><span class="separator"><span /></span></li> <li class="item67 seplink"><span class="separator"><span /></span></li> <li class="item68 seplink"><span class="separator"><span /></span></li> </ul> </li> <li class="item71 seplink"><span class="separator"><span>Help</span></span></li> </ul> How can I achieve this using PHP or even a jQuery solution will be fine. Kindly help.

    Read the article

  • Wireless cuts out on Toshiba Satellite S7208

    - by alecRN
    I recently got a Toshiba Satellite L875-S7208 with Windows 7 preinstalled. I installed Ubuntu 12.04 LTS dual boot to the same Windows partition. However, usually 15 minutes or less after booting, the wifi connection dies. Here's some hopefully relevant information: lspci -knn 00:00.0 Host bridge [0600]: Intel Corporation 2nd Generation Core Processor Family DRAM Controller [8086:0104] (rev 09) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: agpgart-intel 00:02.0 VGA compatible controller [0300]: Intel Corporation 2nd Generation Core Processor Family Integrated Graphics Controller [8086:0116] (rev 09) Subsystem: Toshiba America Info Systems Device [1179:fb40] Kernel driver in use: i915 Kernel modules: i915 00:14.0 USB controller [0c03]: Intel Corporation Panther Point USB xHCI Host Controller [8086:1e31] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: xhci_hcd 00:16.0 Communication controller [0780]: Intel Corporation Panther Point MEI Controller #1 [8086:1e3a] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: mei Kernel modules: mei 00:1a.0 USB controller [0c03]: Intel Corporation Panther Point USB Enhanced Host Controller #2 [8086:1e2d] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: ehci_hcd 00:1b.0 Audio device [0403]: Intel Corporation Panther Point High Definition Audio Controller [8086:1e20] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb40] Kernel driver in use: snd_hda_intel Kernel modules: snd-hda-intel 00:1c.0 PCI bridge [0604]: Intel Corporation Panther Point PCI Express Root Port 1 [8086:1e10] (rev c4) Kernel driver in use: pcieport Kernel modules: shpchp 00:1c.1 PCI bridge [0604]: Intel Corporation Panther Point PCI Express Root Port 2 [8086:1e12] (rev c4) Kernel driver in use: pcieport Kernel modules: shpchp 00:1c.2 PCI bridge [0604]: Intel Corporation Panther Point PCI Express Root Port 3 [8086:1e14] (rev c4) Kernel driver in use: pcieport Kernel modules: shpchp 00:1d.0 USB controller [0c03]: Intel Corporation Panther Point USB Enhanced Host Controller #1 [8086:1e26] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: ehci_hcd 00:1f.0 ISA bridge [0601]: Intel Corporation Panther Point LPC Controller [8086:1e59] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel modules: iTCO_wdt 00:1f.2 SATA controller [0106]: Intel Corporation Panther Point 6 port SATA Controller [AHCI mode] [8086:1e03] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel driver in use: ahci 00:1f.3 SMBus [0c05]: Intel Corporation Panther Point SMBus Controller [8086:1e22] (rev 04) Subsystem: Toshiba America Info Systems Device [1179:fb41] Kernel modules: i2c-i801 02:00.0 Network controller [0280]: Realtek Semiconductor Co., Ltd. RTL8188CE 802.11b/g/n WiFi Adapter [10ec:8176] (rev 01) Subsystem: Realtek Semiconductor Co., Ltd. Device [10ec:8211] Kernel driver in use: rtl8192ce Kernel modules: rtl8192ce 03:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller [10ec:8136] (rev 05) Subsystem: Toshiba America Info Systems Device [1179:fb37] Kernel driver in use: r8169 Kernel modules: r8169 lsmod Module Size Used by snd_hda_codec_hdmi 32474 1 snd_hda_codec_realtek 224066 1 joydev 17693 0 rfcomm 47604 0 bnep 18281 2 bluetooth 180104 10 rfcomm,bnep parport_pc 32866 0 ppdev 17113 0 arc4 12529 2 snd_hda_intel 33773 3 snd_hda_codec 127706 3 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel snd_hwdep 13668 1 snd_hda_codec snd_pcm 97188 3 snd_hda_codec_hdmi,snd_hda_intel,snd_hda_codec snd_seq_midi 13324 0 snd_rawmidi 30748 1 snd_seq_midi snd_seq_midi_event 14899 1 snd_seq_midi snd_seq 61896 2 snd_seq_midi,snd_seq_midi_event snd_timer 29990 2 snd_pcm,snd_seq snd_seq_device 14540 3 snd_seq_midi,snd_rawmidi,snd_seq psmouse 87692 0 serio_raw 13211 0 rtl8192ce 84826 0 rtl8192c_common 75767 1 rtl8192ce rtlwifi 111202 1 rtl8192ce mac80211 506816 3 rtl8192ce,rtl8192c_common,rtlwifi snd 78855 16 snd_hda_codec_hdmi,snd_hda_codec_realtek,snd_hda_intel,snd_hda_codec,snd_hwdep,snd_pcm,snd_rawmidi,snd_seq,snd_timer,snd_seq_device sparse_keymap 13890 0 uvcvideo 72627 0 videodev 98259 1 uvcvideo v4l2_compat_ioctl32 17128 1 videodev mac_hid 13253 0 mei 41616 0 wmi 19256 0 soundcore 15091 1 snd i915 472941 3 snd_page_alloc 18529 2 snd_hda_intel,snd_pcm drm_kms_helper 46978 1 i915 cfg80211 205544 2 rtlwifi,mac80211 drm 242038 4 i915,drm_kms_helper i2c_algo_bit 13423 1 i915 video 19596 1 i915 lp 17799 0 parport 46562 3 parport_pc,ppdev,lp r8169 62099 0 ums_realtek 18248 0 uas 18180 0 usb_storage 49198 1 ums_realtek dmesg | grep firmware [ 15.692951] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 16.240881] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 452.419288] rtl8192c_common:rtl92c_firmware_selfreset(): 8051 reset fail. [ 458.572211] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 465.440640] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 472.337617] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 479.175471] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 485.978582] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 492.764893] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 499.579348] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 506.386934] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 513.209545] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 519.991365] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 526.778375] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 533.629695] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 540.426004] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 547.238125] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 554.024434] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 560.854794] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 567.678160] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 574.494666] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 581.336653] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 588.157710] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 595.221122] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 602.047429] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 608.829534] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 615.639079] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 622.454991] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 629.273231] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 636.056613] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 642.858096] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 649.640753] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 657.184094] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 664.008018] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 670.838639] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 677.675418] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 684.507255] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 691.310994] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 698.095325] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 704.914509] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin [ 711.725178] rtl8192c_common: Loading firmware file rtlwifi/rtl8192cfw.bin uname -r 3.2.0-29-generic ifconfig eth0 Link encap:Ethernet HWaddr 4c:72:b9:59:6c:61 inet addr:192.168.0.11 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::4e72:b9ff:fe59:6c61/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4447 errors:0 dropped:0 overruns:0 frame:0 TX packets:2762 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3671147 (3.6 MB) TX bytes:335133 (335.1 KB) Interrupt:42 Base address:0x2000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:515 errors:0 dropped:0 overruns:0 frame:0 TX packets:515 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:83153 (83.1 KB) TX bytes:83153 (83.1 KB) wlan0 Link encap:Ethernet HWaddr 74:e5:43:32:47:95 UP BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:280 errors:0 dropped:0 overruns:0 frame:0 TX packets:51 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:32958 (32.9 KB) TX bytes:10431 (10.4 KB)

    Read the article

  • Subclassing to avoid line length

    - by Super User
    The standard line length of code is 80 characters per line. This is accepted and followed by the most of programmers. I working on a state machine of a character and is necessary for me follow this too. I have four classes who pass this limit. I can subclass each class in two more and then avoid the line length limit. class Stand class Walk class Punch class Crouch The new classes would be StandLeft, StandRight and so on. Stand, Walk, Punch and Crouch would be then abstract classes. The question if there is a limit for the long of the hierarchies tree or this is depends of the case.

    Read the article

  • c++ defining a static member of a template class with type inner class pointer

    - by Jack
    I have a template class like here (in a header) with a inner class and a static member of type pointer to inner class template <class t> class outer { class inner { int a; }; static inner *m; }; template <class t> outer <t>::inner *outer <t>::m; when i want to define that static member i says "error: expected constructor, destructor, or type conversion before '*' token" on the last line (mingw32-g++ 3.4.5)

    Read the article

  • Class.Class vs Namespace.Class for top level general use class libraries?

    - by Joan Venge
    Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

    Read the article

  • "Class ref in pre-verified class resolved to unexpected implementation" when running android tests i

    - by Mike
    I have a module that builds an app called MyApp. I have another that builds some testcases for that app, called MyAppTests. They both build their own APKs, and they both work fine from within my IDE. I'd like to build them using ant so that I can take advantage of continuous integration. Building the app module works fine. I'm having difficulty getting the Test module to compile and run. Using Christopher's tip from a previous question, I used android create test-project -p MyAppTests -m ../MyApp -n MyAppTests to create the necessary build files to build and run my test project. This seems to work great (once I remove an unnecessary test case that it constructed for me and revert my AndroidManifest.xml to the one I was using before it got replaced by android create), but I have two problems. The first problem: The project doesn't compile because it's missing libraries. $ ant run-tests Buildfile: build.xml [setup] Project Target: Google APIs [setup] Vendor: Google Inc. [setup] Platform Version: 1.6 [setup] API level: 4 [setup] WARNING: No minSdkVersion value set. Application will install on all Android versions. -install-tested-project: [setup] Project Target: Google APIs [setup] Vendor: Google Inc. [setup] Platform Version: 1.6 [setup] API level: 4 [setup] WARNING: No minSdkVersion value set. Application will install on all Android versions. -compile-tested-if-test: -dirs: [echo] Creating output directories if needed... -resource-src: [echo] Generating R.java / Manifest.java from the resources... -aidl: [echo] Compiling aidl files into Java classes... compile: [javac] Compiling 1 source file to /Users/mike/Projects/myapp/android/MyApp/bin/classes -dex: [echo] Converting compiled files and external libraries into /Users/mike/Projects/myapp/android/MyApp/bin/classes.dex... [echo] -package-resources: [echo] Packaging resources [aaptexec] Creating full resource package... -package-debug-sign: [apkbuilder] Creating MyApp-debug-unaligned.apk and signing it with a debug key... [apkbuilder] Using keystore: /Users/mike/.android/debug.keystore debug: [echo] Running zip align on final apk... [echo] Debug Package: /Users/mike/Projects/myapp/android/MyApp/bin/MyApp-debug.apk install: [echo] Installing /Users/mike/Projects/myapp/android/MyApp/bin/MyApp-debug.apk onto default emulator or device... [exec] 1567 KB/s (288354 bytes in 0.179s) [exec] pkg: /data/local/tmp/MyApp-debug.apk [exec] Success -compile-tested-if-test: -dirs: [echo] Creating output directories if needed... [mkdir] Created dir: /Users/mike/Projects/myapp/android/MyAppTests/gen [mkdir] Created dir: /Users/mike/Projects/myapp/android/MyAppTests/bin [mkdir] Created dir: /Users/mike/Projects/myapp/android/MyAppTests/bin/classes -resource-src: [echo] Generating R.java / Manifest.java from the resources... -aidl: [echo] Compiling aidl files into Java classes... compile: [javac] Compiling 5 source files to /Users/mike/Projects/myapp/android/MyAppTests/bin/classes [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:4: package roboguice.test does not exist [javac] import roboguice.test.RoboUnitTestCase; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:8: package com.google.gson does not exist [javac] import com.google.gson.JsonElement; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:9: package com.google.gson does not exist [javac] import com.google.gson.JsonParser; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:11: cannot find symbol [javac] symbol: class RoboUnitTestCase [javac] public class GsonTest extends RoboUnitTestCase<MyApplication> { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:6: package roboguice.test does not exist [javac] import roboguice.test.RoboUnitTestCase; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:7: package roboguice.util does not exist [javac] import roboguice.util.RoboLooperThread; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:11: package com.google.gson does not exist [javac] import com.google.gson.JsonObject; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:15: cannot find symbol [javac] symbol: class RoboUnitTestCase [javac] public class HttpTest extends RoboUnitTestCase<MyApplication> { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/LinksTest.java:4: package roboguice.test does not exist [javac] import roboguice.test.RoboUnitTestCase; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/LinksTest.java:12: cannot find symbol [javac] symbol: class RoboUnitTestCase [javac] public class LinksTest extends RoboUnitTestCase<MyApplication> { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:4: package roboguice.test does not exist [javac] import roboguice.test.RoboUnitTestCase; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:5: package roboguice.util does not exist [javac] import roboguice.util.RoboAsyncTask; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:6: package roboguice.util does not exist [javac] import roboguice.util.RoboLooperThread; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:12: cannot find symbol [javac] symbol: class RoboUnitTestCase [javac] public class SafeAsyncTest extends RoboUnitTestCase<MyApplication> { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectResource': class file for roboguice.inject.InjectResource not found [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectResource' [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectView': class file for roboguice.inject.InjectView not found [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectView' [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectView' [javac] /Users/mike/Projects/myapp/android/MyApp/bin/classes/com/myapp/activity/Stories.class: warning: Cannot find annotation method 'value()' in type 'roboguice.inject.InjectView' [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:15: cannot find symbol [javac] symbol : class JsonParser [javac] location: class com.myapp.test.GsonTest [javac] final JsonParser parser = new JsonParser(); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:15: cannot find symbol [javac] symbol : class JsonParser [javac] location: class com.myapp.test.GsonTest [javac] final JsonParser parser = new JsonParser(); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:18: cannot find symbol [javac] symbol : class JsonElement [javac] location: class com.myapp.test.GsonTest [javac] final JsonElement e = parser.parse(s); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/GsonTest.java:20: cannot find symbol [javac] symbol : class JsonElement [javac] location: class com.myapp.test.GsonTest [javac] final JsonElement e2 = parser.parse(s2); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:19: cannot find symbol [javac] symbol : method getInstrumentation() [javac] location: class com.myapp.test.HttpTest [javac] assertEquals("MyApp", getInstrumentation().getTargetContext().getResources().getString(com.myapp.R.string.app_name)); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:62: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.HttpTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:82: cannot find symbol [javac] symbol : method assertTrue(java.lang.String,boolean) [javac] location: class com.myapp.test.HttpTest [javac] assertTrue(result[0], result[0].contains("Search")); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:87: cannot find symbol [javac] symbol : class JsonObject [javac] location: class com.myapp.test.HttpTest [javac] final JsonObject[] result = {null}; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:90: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.HttpTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:117: cannot find symbol [javac] symbol : class JsonObject [javac] location: class com.myapp.test.HttpTest [javac] final JsonObject[] result = {null}; [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/HttpTest.java:120: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.HttpTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/LinksTest.java:27: cannot find symbol [javac] symbol : method assertTrue(boolean) [javac] location: class com.myapp.test.LinksTest [javac] assertTrue(m.matches()); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/LinksTest.java:28: cannot find symbol [javac] symbol : method assertEquals(java.lang.String,java.lang.String) [javac] location: class com.myapp.test.LinksTest [javac] assertEquals( map.get(url), m.group(1) ); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:19: cannot find symbol [javac] symbol : method getInstrumentation() [javac] location: class com.myapp.test.SafeAsyncTest [javac] assertEquals("MyApp", getInstrumentation().getTargetContext().getString(com.myapp.R.string.app_name)); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:27: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.SafeAsyncTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:65: cannot find symbol [javac] symbol : method assertEquals(com.myapp.test.SafeAsyncTest.State,com.myapp.test.SafeAsyncTest.State) [javac] location: class com.myapp.test.SafeAsyncTest [javac] assertEquals(State.TEST_SUCCESS,state[0]); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:74: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.SafeAsyncTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:105: cannot find symbol [javac] symbol : method assertEquals(com.myapp.test.SafeAsyncTest.State,com.myapp.test.SafeAsyncTest.State) [javac] location: class com.myapp.test.SafeAsyncTest [javac] assertEquals(State.TEST_SUCCESS,state[0]); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:113: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.SafeAsyncTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:144: cannot find symbol [javac] symbol : method assertEquals(com.myapp.test.SafeAsyncTest.State,com.myapp.test.SafeAsyncTest.State) [javac] location: class com.myapp.test.SafeAsyncTest [javac] assertEquals(State.TEST_SUCCESS,state[0]); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:154: cannot find symbol [javac] symbol : class RoboLooperThread [javac] location: class com.myapp.test.SafeAsyncTest [javac] new RoboLooperThread() { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java:187: cannot find symbol [javac] symbol : method assertEquals(com.myapp.test.SafeAsyncTest.State,com.myapp.test.SafeAsyncTest.State) [javac] location: class com.myapp.test.SafeAsyncTest [javac] assertEquals(State.TEST_SUCCESS,state[0]); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/StoriesTest.java:11: cannot access roboguice.activity.GuiceListActivity [javac] class file for roboguice.activity.GuiceListActivity not found [javac] public class StoriesTest extends ActivityUnitTestCase<Stories> { [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/StoriesTest.java:21: cannot access roboguice.application.GuiceApplication [javac] class file for roboguice.application.GuiceApplication not found [javac] setApplication( new MyApplication( getInstrumentation().getTargetContext() ) ); [javac] ^ [javac] /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/StoriesTest.java:22: incompatible types [javac] found : com.myapp.activity.Stories [javac] required: android.app.Activity [javac] final Activity activity = startActivity(intent, null, null); [javac] ^ [javac] 39 errors [javac] 6 warnings BUILD FAILED /opt/local/android-sdk-mac/platforms/android-1.6/templates/android_rules.xml:248: Compile failed; see the compiler error output for details. Total time: 24 seconds That's not a hard problem to solve. I'm not sure it's the right thing to do, but I copied the missing libraries (roboguice and gson) from the MyApp/libs directory to the MyAppTests/libs directory and everything seems to compile fine. But that leads to the second problem, which I'm currently stuck on. The tests compile fine but they won't run: $ cp ../MyApp/libs/gson-r538.jar libs/ $ cp ../MyApp/libs/roboguice-1.1-SNAPSHOT.jar libs/ 0 10:23 /Users/mike/Projects/myapp/android/MyAppTests $ ant run-testsBuildfile: build.xml [setup] Project Target: Google APIs [setup] Vendor: Google Inc. [setup] Platform Version: 1.6 [setup] API level: 4 [setup] WARNING: No minSdkVersion value set. Application will install on all Android versions. -install-tested-project: [setup] Project Target: Google APIs [setup] Vendor: Google Inc. [setup] Platform Version: 1.6 [setup] API level: 4 [setup] WARNING: No minSdkVersion value set. Application will install on all Android versions. -compile-tested-if-test: -dirs: [echo] Creating output directories if needed... -resource-src: [echo] Generating R.java / Manifest.java from the resources... -aidl: [echo] Compiling aidl files into Java classes... compile: [javac] Compiling 1 source file to /Users/mike/Projects/myapp/android/MyApp/bin/classes -dex: [echo] Converting compiled files and external libraries into /Users/mike/Projects/myapp/android/MyApp/bin/classes.dex... [echo] -package-resources: [echo] Packaging resources [aaptexec] Creating full resource package... -package-debug-sign: [apkbuilder] Creating MyApp-debug-unaligned.apk and signing it with a debug key... [apkbuilder] Using keystore: /Users/mike/.android/debug.keystore debug: [echo] Running zip align on final apk... [echo] Debug Package: /Users/mike/Projects/myapp/android/MyApp/bin/MyApp-debug.apk install: [echo] Installing /Users/mike/Projects/myapp/android/MyApp/bin/MyApp-debug.apk onto default emulator or device... [exec] 1396 KB/s (288354 bytes in 0.201s) [exec] pkg: /data/local/tmp/MyApp-debug.apk [exec] Success -compile-tested-if-test: -dirs: [echo] Creating output directories if needed... -resource-src: [echo] Generating R.java / Manifest.java from the resources... -aidl: [echo] Compiling aidl files into Java classes... compile: [javac] Compiling 5 source files to /Users/mike/Projects/myapp/android/MyAppTests/bin/classes [javac] Note: /Users/mike/Projects/myapp/android/MyAppTests/src/com/myapp/test/SafeAsyncTest.java uses unchecked or unsafe operations. [javac] Note: Recompile with -Xlint:unchecked for details. -dex: [echo] Converting compiled files and external libraries into /Users/mike/Projects/myapp/android/MyAppTests/bin/classes.dex... [echo] -package-resources: [echo] Packaging resources [aaptexec] Creating full resource package... -package-debug-sign: [apkbuilder] Creating MyAppTests-debug-unaligned.apk and signing it with a debug key... [apkbuilder] Using keystore: /Users/mike/.android/debug.keystore debug: [echo] Running zip align on final apk... [echo] Debug Package: /Users/mike/Projects/myapp/android/MyAppTests/bin/MyAppTests-debug.apk install: [echo] Installing /Users/mike/Projects/myapp/android/MyAppTests/bin/MyAppTests-debug.apk onto default emulator or device... [exec] 1227 KB/s (94595 bytes in 0.075s) [exec] pkg: /data/local/tmp/MyAppTests-debug.apk [exec] Success run-tests: [echo] Running tests ... [exec] [exec] android.test.suitebuilder.TestSuiteBuilder$FailedToCreateTests:INSTRUMENTATION_RESULT: shortMsg=Class ref in pre-verified class resolved to unexpected implementation [exec] INSTRUMENTATION_RESULT: longMsg=java.lang.IllegalAccessError: Class ref in pre-verified class resolved to unexpected implementation [exec] INSTRUMENTATION_CODE: 0 BUILD SUCCESSFUL Total time: 38 seconds Any idea what's causing the "Class ref in pre-verified class resolved to unexpected implementation" error?

    Read the article

  • in python: can i pass class method as and a default argument to another class method

    - by alex
    i want to to pass class method as and a default argument to another class method, so that i can re-use the method as a @classmethod @classmethod class foo: def func1(self,x): do somthing; def func2(self, aFunc = self.func1): # make some a call to afunc afunc(4) this why when the method func2 is called within the class aFunc defaults to self.func1, but i can call this same function from outside of the class and pass it a different function at the input. i get NameError: name 'self' is not defined

    Read the article

  • documenting class attributes

    - by intuited
    I'm writing a lightweight class whose attributes are intended to be publicly accessible, and only sometimes overridden in specific instantiations. There's no provision in the Python language for creating docstrings for class attributes, or any sort of attributes, for that matter. What is the accepted way, should there be one, to document these attributes? Currently I'm doing this sort of thing: class Albatross(object): """A bird with a flight speed exceeding that of an unladen swallow. Attributes: """ flight_speed = 691 __doc__ += """ flight_speed (691) The maximum speed that such a bird can attain. """ nesting_grounds = "Raymond Luxury-Yacht" __doc__ += """ nesting_grounds ("Raymond Luxury-Yacht") The locale where these birds congregate to reproduce. """ def __init__(**keyargs): """Initialize the Albatross from the keyword arguments.""" self.__dict__.update(keyargs) Although this style doesn't seem to be expressly forbidden in the docstring style guidelines, it's also not mentioned as an option. The advantage here is that it provides a way to document attributes alongside their definitions, while still creating a presentable class docstring, and avoiding having to write comments that reiterate the information from the docstring. I'm still kind of annoyed that I have to actually write the attributes twice; I'm considering using the string representations of the values in the docstring to at least avoid duplication of the default values. Is this a heinous breach of the ad hoc community conventions? Is it okay? Is there a better way? For example, it's possible to create a dictionary containing values and docstrings for the attributes and then add the contents to the class __dict__ and docstring towards the end of the class declaration; this would alleviate the need to type the attribute names and values twice. edit: this last idea is, I think, not actually possible, at least not without dynamically building the class from data, which seems like a really bad idea unless there's some other reason to do that. I'm pretty new to python and still working out the details of coding style, so unrelated critiques are also welcome.

    Read the article

  • Method having an abstract class as a parameter

    - by Ferhat
    I have an abstract class A, where I have derived the classes B and C. Class A provides an abstract method DoJOB(), which is implemented by both derived classes. There is a class X which has methods inside, which need to call DoJOB(). The class X may not contain any code like B.DoJOB() or C.DoJOB(). Example: public class X { private A foo; public X(A concrete) { foo = concrete; } public FunnyMethod() { foo.DoJOB(); } } While instantiating class X I want to decide which derived class (B or C) must be used. I thought about passing an instance of B or C using the constructor of X. X kewl = new X(new C()); kewl.FunnyMethod(); //calls C.DoJOB() kewl = new X(new B()); kewl.FunnyMethod(); // calls B.DoJOB() My test showed that declaring a method with a parameter A is not working. Am I missing something? How can I implement this correctly? (A is abstract, it cannot be instantiated)

    Read the article

  • Naming a class that processes orders

    - by p.campbell
    I'm in the midst of refactoring a project. I've recently read Clean Code, and want to heed some of the advice within, with particular interest in Single Responsibility Principle (SRP). Currently, there's a class called OrderProcessor in the context of a manufacturing product order system. This class is currently performs the following routine every n minutes: check database for newly submitted + unprocessed orders (via a Data Layer class already, phew!) gather all the details of the orders mark them as in-process iterate through each to: perform some integrity checking call a web service on a 3rd party system to place the order check status return value of the web service for success/fail email somebody if web service returns fail constantly log to a text file on each operation or possible fail point I've started by breaking out this class into new classes like: OrderService - poor name. This is the one that wakes up every n minutes OrderGatherer - calls the DL to get the order from the database OrderIterator (? seems too forced or poorly named) - OrderPlacer - calls web service to place the order EmailSender Logger I'm struggling to find good names for each class, and implementing SRP in a reasonable way. How could this class be separated into new class with discrete responsibilities?

    Read the article

  • Pointing class property to another class with vectors

    - by jmclem
    I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

    Read the article

  • Gmail page works but won't stop loading

    - by MLW
    When I open the GMail page in Chrome (9.0.597.102) on OS X (10.6.4), the page works fine and is functional, but it often remains in a "Loading" state, with the loading icon active, for extremely long periods of time. Functionally, there is no problem, since everything is accessible, and the problem is intermittent. Sometimes it immediately completes loading, other times it will claim to be "loading" for hours. My date is correct (as set with time.*.apple.com), and I don't have any Google Labs enabled. Does anyone else have this problem, or know the cause and solution?

    Read the article

  • Hide a base class method from derived class, but still visible outside of assembly

    - by clintp
    This is a question about tidyness. The project is already working, I'm satisfied with the design but I have a couple of loose ends that I'd like to tie up. My project has a plugin architecture. The main body of the program dispatches work to the plugins that each reside in their own AppDomain. The plugins are described with an interface, which is used by the main program (to get the signature for invoking DispatchTaskToPlugin) and by the plugins themselves as an API contract: namespace AppServer.Plugin.Common { public interface IAppServerPlugin { void Register(); void DispatchTaskToPlugin(Task t); // Other methods omitted } } In the main body of the program Register() is called so that the plugin can register its callback methods with the base class, and then later DispatchTaskToPlugin() is called to get the plugin running. The plugins themselves are in two parts. There's a base class that implements the framework for the plugin (setup, housekeeping, teardown, etc..). This is where DispatchTaskToPlugin is actually defined: namespace AppServer.Plugin { abstract public class BasePlugin : MarshalByRefObject, AppServer.Plugin.Common.IAppServerPlugin { public void DispatchTaskToPlugin(Task t) { // ... // Eventual call to actual plugin code // } // Other methods omitted } } The actual plugins themselves only need to implement a Register() method (to give the base class the delegates to call eventually) and then their business logic. namespace AppServer.Plugin { public class Plugin : BasePlugin { override public void Register() { // Calls a method in the base class to register itself. } // Various callback methods, business logic, etc... } } Now in the base class (BasePlugin) I've implemented all kinds of convenience methods, collected data, etc.. for the plugins to use. Everything's kosher except for that lingering method DispatchTaskToPlugin(). It's not supposed to be callable from the Plugin class implementations -- they have no use for it. It's only needed by the dispatcher in the main body of the program. How can I prevent the derived classes (Plugin) from seeing the method in the base class (BasePlugin/DispatchTaskToPlugin) but still have it visible from outside of the assembly? I can split hairs and have DispatchTaskToPlugin() throw an exception if it's called from the derived classes, but that's closing the barn door a little late. I'd like to keep it out of Intellisense or possibly have the compiler take care of this for me. Suggestions?

    Read the article

  • Using a class within another class in asp.net

    - by Phil
    In my site I have class A which selects the required page module (blog,content,gallery etc). I also have class B which provides sqlclient database objects and sql statements. If I use class B in a web form via "Imports Class B". I am able to access the contents. I now would like to use class B within class A but am struggling to find the correct syntax for importing it. Please can someone give me a basic example. We are coming from a classic asp background, and used to simply use includes. We are using VB Thanks.

    Read the article

  • making class accessible from class path in dynamic class loading

    - by Noona
    I have a project created in Eclipse, and I defined an interface and a class for dynamic class loading, the class is in the project directory, so I have this code in my project: if (handlerClassName != null) { TypeHandler typeHandler = null; try { typeHandler = (TypeHandler) (Class.forName(handlerClassName).newInstance()); but I get this exception: java.lang.ClassNotFoundException: "handlerClassName" what should I do to make the JVM recognize the class "handlerClassName" in my project? thanks

    Read the article

  • Class Loading Deadlocks

    - by tomas.nilsson
    Mattis follows up on his previous post with one more expose on Class Loading Deadlocks As I wrote in a previous post, the class loading mechanism in Java is very powerful. There are many advanced techniques you can use, and when used wrongly you can get into all sorts of trouble. But one of the sneakiest deadlocks you can run into when it comes to class loading doesn't require any home made class loaders or anything. All you need is classes depending on each other, and some bad luck. First of all, here are some basic facts about class loading: 1) If a thread needs to use a class that is not yet loaded, it will try to load that class 2) If another thread is already loading the class, the first thread will wait for the other thread to finish the loading 3) During the loading of a class, one thing that happens is that the <clinit method of a class is being run 4) The <clinit method initializes all static fields, and runs any static blocks in the class. Take the following class for example: class Foo { static Bar bar = new Bar(); static { System.out.println("Loading Foo"); } } The first time a thread needs to use the Foo class, the class will be initialized. The <clinit method will run, creating a new Bar object and printing "Loading Foo" But what happens if the Bar object has never been used before either? Well, then we will need to load that class as well, calling the Bar <clinit method as we go. Can you start to see the potential problem here? A hint is in fact #2 above. What if another thread is currently loading class Bar? The thread loading class Foo will have to wait for that thread to finish loading. But what happens if the <clinit method of class Bar tries to initialize a Foo object? That thread will have to wait for the first thread, and there we have the deadlock. Thread one is waiting for thread two to initialize class Bar, thread two is waiting for thread one to initialize class Foo. All that is needed for a class loading deadlock is static cross dependencies between two classes (and a multi threaded environment): class Foo { static Bar b = new Bar(); } class Bar { static Foo f = new Foo(); } If two threads cause these classes to be loaded at exactly the same time, we will have a deadlock. So, how do you avoid this? Well, one way is of course to not have these circular (static) dependencies. On the other hand, it can be very hard to detect these, and sometimes your design may depend on it. What you can do in that case is to make sure that the classes are first loaded single threadedly, for example during an initialization phase of your application. The following program shows this kind of deadlock. To help bad luck on the way, I added a one second sleep in the static block of the classes to trigger the unlucky timing. Notice that if you uncomment the "//Foo f = new Foo();" line in the main method, the class will be loaded single threadedly, and the program will terminate as it should. public class ClassLoadingDeadlock { // Start two threads. The first will instansiate a Foo object, // the second one will instansiate a Bar object. public static void main(String[] arg) { // Uncomment next line to stop the deadlock // Foo f = new Foo(); new Thread(new FooUser()).start(); new Thread(new BarUser()).start(); } } class FooUser implements Runnable { public void run() { System.out.println("FooUser causing class Foo to be loaded"); Foo f = new Foo(); System.out.println("FooUser done"); } } class BarUser implements Runnable { public void run() { System.out.println("BarUser causing class Bar to be loaded"); Bar b = new Bar(); System.out.println("BarUser done"); } } class Foo { static { // We are deadlock prone even without this sleep... // The sleep just makes us more deterministic try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Bar b = new Bar(); } class Bar { static { try { Thread.sleep(1000); } catch(InterruptedException e) {} } static Foo f = new Foo(); }

    Read the article

  • Question about casting a class in Java with generics

    - by Florian F
    In Java 6 Class<? extends ArrayList<?>> a = ArrayList.class; gives and error, but Class<? extends ArrayList<?>> b = (Class<? extends ArrayList<?>>)ArrayList.class; gives a warning. Why is (a) an error? What is it, that Java needs to do in the assignment, if not the cast shown in (b)? And why isn't ArrayList compatible with ArrayList? I know one is "raw" and the other is "generic", but what is it you can do with an ArrayList and not with an ArrayList, or the other way around?

    Read the article

  • Java code generation from class diagram

    - by Sanjay
    I'm on the way developing a Java application where user can provide a class diagram and get the corresponding Java code. I don't know how can I let the user interactively draw a class diagram in Java. I am currently getting the required parameters like attributes, functions directly from the user, and then I render a class diagram for him. I show the class diagram on a jdialog. Is there a better way to do this? This is an example of a class diagram, I need to generate this from a Java program, given the values and relationship.

    Read the article

  • Switching from abstract class to interface

    - by nischayn22
    I have an abstract class which has all abstract methods except one which constructs objects of the subclasses. Now my mentor asked me to move this abstract class to an interface. Having an interface is no problem except with the method used to construct subclass objects. Where should this method go now? Also, I read somewhere that interfaces are more efficient than abstract classes. Is this true? Here's an example of my classes abstract class Animal { //many abstract methods getAnimalobject(some parameter) { return //appropriate subclass } } class Dog extends Animal {} class Elephant extends Animal {}

    Read the article

  • C# Cast Class to Overridden Class

    - by Nathan Tornquist
    I have a class Application that I need to override with INotifyPropertyChanged events. I have written the logic to override the original class and ended up creating SuperApplication I am pulling the data from a library though, and cannot change the loading logic. I just need a way to get the data from the original class into my superClass. I've tried things like superClass = (SuperApplication)standardClass; but it hasn't worked. How would I go about doing this? If it helps, this is the code I'm using to override the original class: public class SuperCreditApplication : CreditApplication { public SuperCreditApplicant Applicant { get; set; } public SuperCreditApplicant CoApplicant { get; set; } } public class SuperCreditApplicant : CreditApplicant { public SuperProspect Prospect { get; set; } } public class SuperProspect : Prospect, INotifyPropertyChanged { public State DriverLicenseState { get { return DriverLicenseState; } set { DriverLicenseState = value; OnPropertyChanged("DriverLicenseState"); } } public event PropertyChangedEventHandler PropertyChanged; private void OnPropertyChanged(string propertyName) { if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(propertyName)); } } }

    Read the article

< Previous Page | 1 2 3 4 5 6 7 8 9 10 11 12  | Next Page >