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  • Linux Read-Ahead Downsides

    - by JPerkSter
    Hi Everyone, Hope all is well. I have a question regarding read-ahead caching. Are there any downsides to raising the size of the read-ahead cache? On our farm, we're currently running at 256, and upon raising that higher, we are seeing significant throughput gains.   [root@server~]# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 7352 MB in 2.00 seconds = 3677.62 MB/sec 3 Timing buffered disk reads: 244 MB in 3.10 seconds = 78.68 MB/sec [root@server ~]# blockdev --setra 10240 /dev/sda [root@server ~]# hdparm -tT /dev/sda /dev/sda: Timing cached reads: 11452 MB in 2.00 seconds = 5728.52 MB/sec Timing buffered disk reads: 422 MB in 3.17 seconds = 133.04 MB/sec We are running on 2.6. Thanks!

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  • Hiding "Syntax OK" from apache2ctl output

    - by Oscar Barrett
    I am checking whether a particular apache module is installed using apache2ctl -M. When listing the modules, apache runs a syntax check on the configuration files which prints out "Syntax OK" if everything is fine. However, this message doesn't seem to be coming from STDOUT or STDERR as it shows even if all output is redirected to /dev/null. i.e. $ sudo apache2ctl -M Loaded Modules: core_module (static) log_config_module (static) ... Syntax OK $ sudo apache2ctl -M >/dev/null Syntax OK How is this being outputted, and is it possible to hide?

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  • How can I set deadline as the I/O scheduler for USB Flash devices by using udev rules?

    - by ????
    I have set CFQ as the default I/O scheduler. I often get bad performance when I write data into a Flash device. This is resolved if I use deadline as the I/O scheduler for USB Flash devices. I can't always change the scheduler manually, right? I think writing udev rules is a good idea. Can someone please write rules for me? I want: When I plug in a USB device, detect the type of the device. If it is a portable USB hard disk, do nothing (I think if a device has more than one partitions, it always a portable hard disk. If it is a USB Flash device, set deadline as it's scheduler.

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  • How do I know if my disks are being hit with too many I/O reads or writes or both?

    - by Mark F
    I know a bit about disk I/O and bottlenecks relating to this especially when relating to databases. How do I really know what the max I/O numbers will be for my disks? What metric might be available to me for working out roughly (but needs to be a good approximation) of how much capacity (if you will) have I got left available in I/O. I've seen it before where things are bubbling along nicely and then all of a sudden, everything screams to a halt, and it ends up being an I/O bound problem. Is there a better way to predict when I/O is reaching its limits? This article was interesting but not giving the answer I desire. So, is my best bet surrounding just looking at 'CPU I/O WAIT'? There must be a more reactive method than this.

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  • How to accelerate and notice failure of potentially faulty disks

    - by rainier
    Hey, I got a bunch of 'used' servers, whose disks should have been checked, but they have been shipped around the county in crate which can't help. I just had one disk go bad (despite being mirrored, currently trying to get more details). The server was fine for about a week before everything ground to a halt this afternoon. Is there any way 'accelerate' the failure of faulty disks, with the goal of bringing the disk to failure before we launch production services? Would doing lots of I/O with 'dd' or 'iozone' be a good way to test these potentially faulty disks? Any other tests/tools that would help recognized failures before they happen?

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  • I/O redirection using cygwin and mingw

    - by KLee1
    I have written a program in C and have compiled it using MinGW. When I try to run that program in Cygwin, it seems to behave normally (i.e. prints correct output etc.) However, I'm trying to pipe output to a program so that I can parse information from the program's output. However, the piping does not seem to be working in that I am not getting any input into the second program. I have confirmed this by using the following commands: This command seems to work fine: ./prog Performing this command returns nothing: ./prog | cat This command verifies the first: ./prog | wc Which returns: 0 0 0 I know that the script (including the piping from the program) works perfectly fine in an all Linux environment. Does anyone have any idea for why the piping isn't working in Cygwin? Thanks!

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  • performance monitoring

    - by Sunny
    I want to monitor CPU usage, disk read/write usage for a particular process, say ./myprocess. To monitor CPU top command seems to be a nice option and for read and write iotop seems to be a handy one. For example to monitor read/write for every second i use the command iotop -tbod1 | grep "myprocess". My difficulty is I just want only three variables to store, namely read/sec, write/sec, cpu usage/sec. Could you help me with a script that combines the outputs the above said three variables from top and iotop to be stored into a log file? Thanks!

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  • Full list of top-like tool family for perfomance monitoring in linux: iftop iotop htop atop more? [closed]

    - by Yauhen Yakimovich
    Top-like utilities are extremely handful in my work and I want to make sure I am not missing any of them. Please extend the following list of performance monitoring (top-like) family of linux tools: top - original tool htop - adds support to multicore/cpu iotop - input/output monitoring iftop - network monitoring atop - merges previous elements into a single overview slabtop – displays a listing of the top caches ? The only criteria - maturity and similarity in function/style.

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  • How to increase the disk cache of Windows 7

    - by Mark Christiaens
    Under Windows 7 (64 bit), I'm reading through 9000 moderately sized files. In total, there is more than 200 MB of data. Using Java (JDK 1.6.21) I'm iterating over the files. The first 1400 or so go at full speed but then speed drops off to 4ms per file. It turns out that the main cost is incurred simply by opening the files. I'm opening the files using new FileInputStream (and of course closing them in time to avoid file leaks). After some investigating, I see that Windows' disk cache is using only 100 MB or so of RAM although I have 8 GiB available. I've tried increasing the cache size using the CacheSet tool but any values I provide are considered out of range. I've also tried enabling the LargeSystemCache registry key but (after rebooting) the CacheSet tool still indicates I'm using 100 MB of cache (and doesn't increase during the test run). Does anybody have any suggestions to "encourage" Windows 7 to cache my 9000 files?

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  • Fastest security check of file tree on NFS

    - by fungs
    I am currently experiencing very bad performance using the following on an NFS network folder: time find . | while read f; do test -L "$f" && f=$(readlink -m $f); grp="$(stat -c %G $f)"; perm="$(stat -c %A $f)"; done Question 1) Within the loop permissions are checked using the variables grp and perm. Is there a way to lower the amount of disc I/O for these kind of checks over the network (e.g. read all meta data at once using find)? Question 2) It seems like the NFS isn't tuned very well, the same operation on a similar network link via SSHFS take only one third of the time. All parameters are auto-negotiated. Any suggestions?

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  • random hard disk errors

    - by AugB
    For the past 2 years or so (4 year old custom build) I've been getting random moments where everything stops responding (or takes a very long time to respond) followed by I/O and hdd not detected errors on restart. To fix it, all I usually need to do is unplug my SATA cables from the hdd and mobo and plug them back in again and the problem disappears, at least for a little while (it ranges anywhere from a day to a few months time). Sometimes even a startup repair does the job. I've done multiple reformats and have also ran chkdsk more times than I can remember and both do not seem to help in the long run. Both the drives seem to be exhibiting the same problem. Have both my hdds been "dying" for the past couple of years, even though they are fully functional besides these occasional hiccups? Does the issue lie elsewhere? All feedback is appreciated. System specs: Biostar Tpower i45 mobo 2x WD Caviar 640GB hdds Zalman 750w psu Radeon 5870 gpu 2x2gb Gskill DDR2 ram Win7 64

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  • Need data on disk drive management by OS: getting base I/O unit size, “sync” option, Direct Memory A

    - by Richard T
    Hello All, I want to ensure I have done all I can to configure a system's disks for serious database use. The three areas I know of (any others?) to be concerned about are: I/O size: the database engine and disk's native size should either match, or the database's native I/O size should be a multiple of the disk's native I/O size. Disks that are capable of Direct Memory Access (eg. IDE) should be configured for it. When a disk says it has written data persistently, it must be so! No keeping it in cache and lying about it. I have been looking for information on how to ensure these are so for CENTOS and Ubuntu, but can't seem to find anything at all! I want to be able to check these things and change them if needed. Any and all input appreciated.

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  • Parallel.For System.OutOfMemoryException

    - by Martin Neal
    We have a fairly simple program that's used for creating backups. I'm attempting to parallelize it but am getting an OutofMemoryException within an AggregateExcption. Some of the source folders are quite large, and the program doesn't crash for about 40 minutes after it starts. I don't know where to start looking so the below code is a near exact dump of all code the code sans directory structure and Exception logging code. Any advise as to where to start looking? using System; using System.Diagnostics; using System.IO; using System.Threading.Tasks; namespace SelfBackup { class Program { static readonly string[] saSrc = { "\\src\\dir1\\", //... "\\src\\dirN\\", //this folder is over 6 GB }; static readonly string[] saDest = { "\\dest\\dir1\\", //... "\\dest\\dirN\\", }; static void Main(string[] args) { Parallel.For(0, saDest.Length, i => { try { if (Directory.Exists(sDest)) { //Delete directory first so old stuff gets cleaned up Directory.Delete(sDest, true); } //recursive function clsCopyDirectory.copyDirectory(saSrc[i], sDest); } catch (Exception e) { //standard error logging CL.EmailError(); } }); } } /////////////////////////////////////// using System.IO; using System.Threading.Tasks; namespace SelfBackup { static class clsCopyDirectory { static public void copyDirectory(string Src, string Dst) { Directory.CreateDirectory(Dst); /* Copy all the files in the folder If and when .NET 4.0 is installed, change Directory.GetFiles to Directory.Enumerate files for slightly better performance.*/ Parallel.ForEach<string>(Directory.GetFiles(Src), file => { /* An exception thrown here may be arbitrarily deep into this recursive function there's also a good chance that if one copy fails here, so too will other files in the same directory, so we don't want to spam out hundreds of error e-mails but we don't want to abort all together. Instead, the best solution is probably to throw back up to the original caller of copy directory an move on to the next Src/Dst pair by not catching any possible exception here.*/ File.Copy(file, //src Path.Combine(Dst, Path.GetFileName(file)), //dest true);//bool overwrite }); //Call this function again for every directory in the folder. Parallel.ForEach(Directory.GetDirectories(Src), dir => { copyDirectory(dir, Path.Combine(Dst, Path.GetFileName(dir))); }); } }

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  • fileToSTring keeps on returning " "

    - by karikari
    I managed to get this code to compile with out error. But somehow it did not return the strings that I wrote inside file1.txt and file.txt that I pass its path through str1 and str2. My objective is to use this open source library to measure the similarity between strings contains inside 2 text files. Inside the its Javadoc, its states that ... public static java.lang.StringBuffer fileToString(java.io.File f) private call to load a file and return its content as a string. Parameters: f - a file for which to load its content Returns: a string containing the files contents or "" if empty or not present Here's is my modified code trying to use the FileLoader function, but fails to return the strings inside the file. The end result keeps on returning me the "" . I do not know where is my fault: package uk.ac.shef.wit.simmetrics; import java.io.File; import uk.ac.shef.wit.simmetrics.similaritymetrics.*; import uk.ac.shef.wit.simmetrics.utils.*; public class SimpleExample { public static void main(final String[] args) { if(args.length != 2) { usage(); } else { String str1 = "arg[0]"; String str2 = "arg[1]"; File objFile1 = new File(str1); File objFile2 = new File(str2); FileLoader obj1 = new FileLoader(); FileLoader obj2 = new FileLoader(); str1 = obj1.fileToString(objFile1).toString(); str2 = obj2.fileToString(objFile2).toString(); System.out.println(str1); System.out.println(str2); AbstractStringMetric metric = new MongeElkan(); //this single line performs the similarity test float result = metric.getSimilarity(str1, str2); //outputs the results outputResult(result, metric, str1, str2); } } private static void outputResult(final float result, final AbstractStringMetric metric, final String str1, final String str2) { System.out.println("Using Metric " + metric.getShortDescriptionString() + " on strings \"" + str1 + "\" & \"" + str2 + "\" gives a similarity score of " + result); } private static void usage() { System.out.println("Performs a rudimentary string metric comparison from the arguments given.\n\tArgs:\n\t\t1) String1 to compare\n\t\t2)String2 to compare\n\n\tReturns:\n\t\tA standard output (command line of the similarity metric with the given test strings, for more details of this simple class please see the SimpleExample.java source file)"); } }

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  • Java Can't Find File when Running through Eclipse

    - by derekerdmann
    When I run a Java application that should be reading from a file in Eclipse, I get a java.io.FileNotFoundException, even though the file is in the correct directory. I can compile and run the application from the command line just fine; the problem only occurs in Eclipse, with more than one project and application. Is there a setting I need to change in the run configurations or build paths to get it to find the file correctly?

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  • Create all directories up to a point?

    - by Stefan Kendall
    I need to be able to build all directories up to and including the directory specified by my File object. For example, suppose I have something like this: File file = new File( "/var/a/b/c/d/" ); But only /var/ exists. I need a method that builds up to d, and I was wondering if there was a method in a java io library somewhere that does this already.

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  • C#, how to delete all files and folders in a directory?

    - by JL
    Using C#, how can I delete all files and folders from a directory, but still keep the root directory? I have this System.IO.DirectoryInfo downloadedMessageInfo = new DirectoryInfo(GetMessageDownloadFolderPath()); foreach (FileInfo file in downloadedMessageInfo.GetFiles()) { file.Delete(); } foreach (DirectoryInfo dir in downloadedMessageInfo.GetDirectories()) { dir.Delete(true); } Is this the cleanest way to do it?

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  • Java: Check if file is already open

    - by hello_world_infinity
    I need to write a custom batch File renamer. I've got the bulk of it done except I can't figure out how to check if a file is already open. I'm just using the java.io.File package and there is a canWrite() method but that doesn't seem to test if the file is in use by another program. Any ideas on how I can make this work?

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  • Is there a common way to access files, that works both on android and PC?

    - by m01
    Hi, I'm writing an application that will ship in two versions: Android and PC version. Is there a simple way to access files from the shared code? Using java.io is simple, but I don't know how to access android resources or assets using it. And I can't write methods that operate on FileInputStreams instead, because some files contain references to another ones, so I need a way to access them from the method code. Any suggestions?

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  • How to read a file from bottom to top in Ruby?

    - by two2twelve
    I've been working on a log viewer for a Rails app and have found that I need to read around 200 lines of a log file from bottom to top instead of the default top to bottom. Log files can get quite large, so I've already tried and ruled out the IO.readlines("log_file.log")[-200..-1] method. Are there any other ways to go about reading a file backwards in Ruby without the need for a plugin or gem?

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  • Nullpointerexcption & abrupt IOStream closure with inheritence and subclasses

    - by user1401652
    A brief background before so we can communicate on the same wave length. I've had about 8-10 university courses on programming from data structure, to one on all languages, to specific ones such as java & c++. I'm a bit rusty because i usually take 2-3 month breaks from coding. This is a personal project that I started thinking of two years back. Okay down to the details, and a specific question, I'm having problems with my mutator functions. It seems to be that I am trying to access a private variable incorrectly. The question is, am I nesting my classes too much and trying to mutate a base class variable the incorrect way. If so point me in the way of the correct literature, or confirm this is my problem so I can restudy this information. Thanks package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Date { private int hour, minute, day, month, year; Date() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What's the hour? (Use 1-24 military notation"); hour = Integer.parseInt(keyboard.readLine()); System.out.println("what's the minute? "); minute = Integer.parseInt(keyboard.readLine()); System.out.println("What's the day of the month?"); day = Integer.parseInt(keyboard.readLine()); System.out.println("Which month of the year is it, use an integer"); month = Integer.parseInt(keyboard.readLine()); System.out.println("What year is it?"); year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (IOException e) { System.out.println("Yo houston we have a problem"); } } public void setHour(int hour) { this.hour = hour; } public void setHour() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What hour, use military notation?"); this.hour = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getHour() { return hour; } public void setMinute(int minute) { this.minute = minute; } public void setMinute() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What minute?"); this.minute = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ": doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": minute shall not cooperate"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the setMinute function of the Date class"); } } public int getMinute() { return minute; } public void setDay(int day) { this.day = day; } public void setDay() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What day 0-6?"); this.day = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getDay() { return day; } public void setMonth(int month) { this.month = month; } public void setMonth() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What month 0-11?"); this.month = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getMonth() { return month; } public void setYear(int year) { this.year = year; } public void setYear() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What year?"); this.year = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getYear() { return year; } public void set() { setMinute(); setHour(); setDay(); setMonth(); setYear(); } public Vector<Integer> get() { Vector<Integer> holder = new Vector<Integer>(5); holder.add(hour); holder.add(minute); holder.add(month); holder.add(day); holder.add(year); return holder; } }; That is the Date class obviously, next is the other base class Location. package GroceryReceiptProgram; import java.io.*; import java.util.Vector; public class Location { String streetName, state, city, country; int zipCode, address; Location() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What is the street name"); streetName = keyboard.readLine(); System.out.println("Which state?"); state = keyboard.readLine(); System.out.println("Which city?"); city = keyboard.readLine(); System.out.println("Which country?"); country = keyboard.readLine(); System.out.println("Which zipcode?");//if not u.s. continue around this step zipCode = Integer.parseInt(keyboard.readLine()); System.out.println("What address?"); address = Integer.parseInt(keyboard.readLine()); } catch (IOException e) { System.out.println(e.toString()); } } public void setZipCode(int zipCode) { this.zipCode = zipCode; } public void setZipCode() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What zipCode?"); this.zipCode = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public void set() { setAddress(); setCity(); setCountry(); setState(); setStreetName(); setZipCode(); } public int getZipCode() { return zipCode; } public void setAddress(int address) { this.address = address; } public void setAddress() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.address = Integer.parseInt(keyboard.readLine()); keyboard.close(); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString()); } } public int getAddress() { return address; } public void setStreetName(String streetName) { this.streetName = streetName; } public void setStreetName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.streetName = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getStreetName() { return streetName; } public void setState(String state) { this.state = state; } public void setState() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.state = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getState() { return state; } public void setCity(String city) { this.city = city; } public void setCity() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.city = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCity() { return city; } public void setCountry(String country) { this.country = country; } public void setCountry() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.country = keyboard.readLine(); keyboard.close(); } catch (IOException e) { System.out.println(e.toString()); } } public String getCountry() { return country; } }; their parent(What is the proper name?) class package GroceryReceiptProgram; import java.io.*; public class FoodGroup { private int price, count; private Date purchaseDate, expirationDate; private Location location; private String name; public FoodGroup() { try { setPrice(); setCount(); expirationDate.set(); purchaseDate.set(); location.set(); } catch (NullPointerException e) { System.out.println(e.toString() + ": in the constructor of the FoodGroup class"); } } public void setPrice(int price) { this.price = price; } public void setPrice() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What Price?"); price = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setPrice function"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class. SetPrice()"); } } public int getPrice() { return price; } public void setCount(int count) { this.count = count; } public void setCount() { try (BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in))) { System.out.println("What count?"); count = Integer.parseInt(keyboard.readLine()); } catch (NumberFormatException e) { System.out.println(e.toString() + ":doesnt seem to be a number"); } catch (IOException e) { System.out.println(e.toString() + ": in the FoodGroup class, setCount()"); } catch (NullPointerException e) { System.out.println(e.toString() + ": in FoodGroup class, setCount"); } } public int getCount() { return count; } public void setName(String name) { this.name = name; } public void setName() { try { BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in)); System.out.println("What minute?"); this.name = keyboard.readLine(); } catch (IOException e) { System.out.println(e.toString()); } } public String getName() { return name; } public void setLocation(Location location) { this.location = location; } public Location getLocation() { return location; } public void setPurchaseDate(Date purchaseDate) { this.purchaseDate = purchaseDate; } public void setPurchaseDate() { this.purchaseDate.set(); } public Date getPurchaseDate() { return purchaseDate; } public void setExpirationDate(Date expirationDate) { this.expirationDate = expirationDate; } public void setExpirationDate() { this.expirationDate.set(); } public Date getExpirationDate() { return expirationDate; } } and finally the main class, so I can get access to all of this work. package GroceryReceiptProgram; public class NewMain { public static void main(String[] args) { FoodGroup test = new FoodGroup(); } } If anyone is further interested, here is a link the UML for this. https://www.dropbox.com/s/1weigjnxih70tbv/GRP.dia

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