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• having problems in running my java program..

  - by Tarun

  I'm a beginner in java so this question might seem a little stupid, my jdk and jre are installed in C:\program files, I write my program and save it in in my folder G:\start, now my program compiles without any error(the .class file is also generated), but when i run my program it says "unable to locate G:\lib\amd64\jvm.cfg", so i copy the 'lib' folder from my jdk folder and paste it in G:, again program compiles without any error, but when i run it,it gives my a new error saying "unable to locate G:\bin\server\jvm.dll",so i copy the 'bin' folder to g:, but now when i run, it gives me the same error again "unable to locate G:\bin\server\jvm.dll",where am I going wrong?

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• Java Inheritance Concept Understanding

  - by Nirmal

  Hello All.... I am just refreshing the oops features of the java. So, I have a little confusion regarding inheritance concept. For that I have a following sample code : class Super{ int index = 5; public void printVal(){ System.out.println("Super"); } } class Sub extends Super{ int index = 2; public void printVal(){ System.out.println("Sub"); } } public class Runner { public static void main(String args[]){ Super sup = new Sub(); System.out.println(sup.index+","); sup.printVal(); } } Now above code is giving me output as : 5,Sub. Here, we are overriding printVal() method, so that is understandable that it is accessing child class method only. But I could not understand why it's accessing the value of x from Super class... Thanks in advance....

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• How do I calculate someone's age in Java?

  - by nojevive

  I want to return an age in years as an int in a Java method. What I have now is the following where getBirthDate() returns a Date object (with the birth date ;-)): public int getAge() { long ageInMillis = new Date().getTime() - getBirthDate().getTime(); Date age = new Date(ageInMillis); return age.getYear(); } But since getYear() is deprecated I'm wondering if there is a better way to do this? I'm not even sure this works correctly, since I have no unit tests in place (yet).

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• Java - Optimize finding a string in a list

  - by Mark

  I have an ArrayList of objects where each object contains a string 'word' and a date. I need to check to see if the date has passed for a list of 500 words. The ArrayList could contain up to a million words and dates. The dates I store as integers, so the problem I have is attempting to find the word I am looking for in the ArrayList. Is there a way to make this faster? In python I have a dict and mWords['foo'] is a simple lookup without looping through the whole 1 million items in the mWords array. Is there something like this in java? for (int i = 0; i < mWords.size(); i++) { if ( word == mWords.get(i).word ) { mLastFindIndex = i; return mWords.get(i); } }

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• C++ / Java: Toggle boolean statement?

  - by Martijn Courteaux

  Hi, Is there a short way to toggle a boolean? With integers we can do operations like this: int i = 4; i *= 4; // equals 16 /* Which is equivalent to */ i = i * 4; So is there also something for booleans (like the *= operator for ints)? In C++: bool booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something? In Java: boolean booleanWithAVeryLongName = true; booleanWithAVeryLongName = !booleanWithAVeryLongName; // Can it shorter? booleanWithAVeryLongName !=; // Or something?

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• Java Sql Udate error, data type missmatch

  - by codo

  I have created a table in ms access. I have set the data type of ID to Auto Number in MS-access. In java when I try to update a record. the netBeans IDE gives me the error of " data type missmatch in criteria expression". But when I changed the ID number that was not in the table already it works well. The code is below. String sql = "Update table1 set price ='" + txtPrice.getText() + "', quantity='" + txtQuantity.getText() + "', description='" + txtDescription.getText() + "' where id= " + txtid.getText() + ""; try { pst = conn.prepareStatement(sql); pst.executeUpdate(); JOptionPane.showMessageDialog(null, "Updated"); UpdateJTable(); } catch (Exception e) { JOptionPane.showMessageDialog(null, e); }

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• identify the input that is multiple of 11 and odd or even java

  - by Bolor Ch

  i am trying to write code to determine the nature of input using if statement only. The nature of input could be following: a multiple of 11 even or odd. For the code below, when I enter my input, it does not display the result as "input:NOT:ODD". Also how can I check multiple conditions with if statement? (else is not considered) import java.util.Scanner; public class test { public static void main( String args[] ) { Scanner input = new Scanner( System.in ); int x; int EO; int Mult; System.out.print ( "Enter value: " ); x = input.nextInt(); EO = x % 2; Mult = x % 11; if (EO > 0 && Mult > 0) { System.out.printf ("%d:NOT:ODD"); } } }

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• are Hierarchical SIngletons in Java possible?

  - by Zach H

  I've been toying with an interesting idea (No idea if I'll include it in any code, but it's fun to think about) Let's say we have a program that requires a large number of classes, all of a certain subclass. And those classes all need to be singletons. Now, we could write the singleton pattern for each of those classes, but it seems wasteful to write the same code over and over, and we already have a common base class. It would be really nice to create a getSingleton method of A that when called from a subclass, returns a singleton of the B class (cast to class A for simplicity) class A{ public A getSingleton(){ //Wizardry } } class B extends A{ } A blargh = B.getSingleton() A gish = B.getSingleton() if(A == B) System.out.println("It works!") It seems to me that the way to do this would be to recognize and call B's default constructor (assuming we don't need to pass anything in.) I know a little of the black magic of reflection in Java, but i'm not sure if this can be done. Anyone interested in puzzling over this?

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• Saving object state on Java without using external memory

  - by TryHarder

  Good day. I know that in order to save object state in Java I should use serialization. But in every single topic about serialization states that I must save my object somewhere (disk, network). My problem is that I'm not allowed to do so. I need a way to save and recover object state without writing it on "external" memory. Maybe to save it on heap or stack... Please don't offer to clone it, I'm not allowed to do so as well. Thanks.

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• Java - jar with librairies included

  - by kozher

  I am currently trying to make a Jar with all my librairies included. What I have done. I have created folders like this : - main folder - class (which contain all my classes) - ressources (containing all my librairies : mongo, jedis...) - MANIFEST.MF My main class is named process. My manifest is like this : Main-Class: processEAN Class-Path: ressources\commons-pool-1.5.6.jar ressources\jedis-2.0.0.jar resources\mongo-2.6.3.jar class - I have generated the JAR with this command : jar cvmf MANIFEST.MF processEAN.jar class/*.class ressources/*.jar My problem : When executing the JAR I have still the message "Exception in thread "main" java.lang.NoClassDefFoundError: processEAN" Any ideas ? Thanks

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• Circle class in java

  - by user292395

  I need to get the Java code for the below problem asap. Create a class Circle that will allow us to define a circle with a specific radius. Your class should include the following methods: A constructor that can create a circle with a specified radius. A method setRadius that sets a specific value as a new radius for an existing circle. A method getRadius that returns the radius of an existing circle. A method toString that returns a String with all the information about an existing circle. A method computeArea that computes the area of a circle A method computePerimeter that computes the perimeter of a circle.

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• Comparing Each Character in Java String

  - by user2760357

  I am a beginner at java, and I am trying to create two strings and compare each character. If there is a matching character or characters, the code has to print out the length of each string, without the matching characters. For example, if one string is "super," and the other is "perfect," the program should interpret the strings as superfect, and print out 9 However, if there is no matching part, like pencil and eraser, the code should printout 12, which is the length of two strings combined. Right now, I am having a problem with comparing each character, since I tried to use if(input_word.compareToIgnoreCase(input_word2) != 0) but it only compared the string as a whole.. any suggestion? Thank you for your efforts

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• NoSuchMethodException while using JAVA Reflection

  - by Appps

  Hi I'm trying to use reflection to invoke a method and update the setter value of that method. But I'm getting NoSuchMethodException while ivoking that method. com.test.Test.setAddress1(java.lang.Double) .But I've this method defined in my Class. Is the problem with my code. Can someone please help me? Thanks in advance. I've my code below. Class[] doubleArrayParamTypes = new Class[ 1 ]; doubleArrayParamTypes[ 0 ] = Double.class; Class class=Class.forName( "com.test.Test"); Object voObject = class.newInstance(); String data="TestData"; performMapping(class,"setAddress1",doubleArrayParamTypes ,voObject,data); /* Reflection to set the data */ private void performMapping(Class class,String methodName,Class[] clazz,Object voObject,Object data) { class.getMethod( "set" + methodName, clazz ).invoke( voObject, data ); }

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• Java JFrame is very strange

  - by rodion

  When I am running this, JLabel is not visible, but when I resize window (with mouse) JLabel is showed. Why? import javax.swing.*; import java.awt.*; public class FrmTaoLogin extends JFrame { private JPanel pnlLeft = new JPanel(); public FrmTaoLogin() { super(); pnlLeft.setBorder(BorderFactory.createEtchedBorder()); pnlLeft.add(new JLabel("test1")); getContentPane().add(pnlLeft,BorderLayout.SOUTH); setDefaultCloseOperation(EXIT_ON_CLOSE); setSize(200, 200); } public static void main(String[] args) { FrmTaoLogin FrmLogin = new FrmTaoLogin(); FrmLogin.setVisible(true); } }

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• Simulating python's With statement in java

  - by drozzy

  Is there something like Python with context manager in Java? For example say I want to do something like the following: getItem(itemID){ Connection c = C.getConnection(); c.open(); try{ Item i = c.query(itemID); }catch(ALLBunchOfErrors){ c.close(); } c.close(); return c; } where in python I just have: with( C.getConnection().open() as c): Item i = c.query(itemID); return i;

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• Adding Timestamp to Java's GC messages in Tomcat 6

  - by ripper234

  I turned on Java's GC log options -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+PrintGCDetails Which print out these messages to standard output (catalina.out): 314.884: [CMS-concurrent-mark-start] 315.014: [CMS-concurrent-mark: 0.129/0.129 secs] [Times: user=0.14 sys=0.00, real=0.13 secs] 315.014: [CMS-concurrent-preclean-start] 315.016: [CMS-concurrent-preclean: 0.003/0.003 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] 315.016: [CMS-concurrent-abortable-preclean-start] 332.055: [GC 332.055: [ParNew: 17128K->84K(19136K), 0.0017700 secs] 88000K->70956K(522176K) icms_dc=4 , 0.0018660 secs] [Times: user=0.00 sys=0.00, real=0.00 secs] CMS: abort preclean due to time 352.253: [CMS-concurrent-abortable-preclean: 0.023/37.237 secs] [Times: user=0.78 sys=0.02, real=37.23 secs] How can I make these log lines appear with an actual timestamp (including date) instead of these numbers, which presumably mean "time since JVM started" ?

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• jEdit+JythonInterpreter: how to import java class?

  - by JChao

  Hi, I'm running jEdit with the JythonInterprete and I have a .jar file called JavaTest.jar. JavaTest has a class called SampleJavaClass which has a method printerCount. From my .py file, I want to do: from javatest import SampleJavaClass class SampleClass(SampleJavaClass): def pymain(self): SampleJavaClass.printerCount(4) Java code: package javatest; public class SampleJavaClass { public static void printerCount(int i){ for(int j=0; j< i; j++){ System.out.println("hello world"); } } (etc...) In the JythonInterpreter, I have already tried clicking "Edit Jython Path" and adding the .jar file then running the interpreter again, but it still gives me ImportError: cannot import name SampleJavaClass

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• Is this valid Java code?

  - by Eric

  I'm using Eclipse, and it is perfectly happy with the following code: public interface MessageType { public static final byte KICK = 0x01; public static final byte US_PING = 0x02; public static final byte GOAL_POS = 0x04; public static final byte SHUTDOWN = 0x08; public static final byte[] MESSAGES = new byte[] { KICK, US_PING, GOAL_POS, SHUTDOWN }; } public class MessageTest implements MessageType { public static void main(String[] args) { int b = MessageType.MESSAGES.length; //Not happy } } However, the platform that I'm running it on crashes at the line marked above. By crash, think an equivalent of a BSOD. Is there anything wrong with my code, or do I need to pursue the developers of the Java VM for my platform?

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• INSERT SQL in Java

  - by Pierre

  Hello. I have a Java application and I want to use SQL database. I have a class for my connection : public class SQLConnection{ private static String url = "jdbc:postgresql://localhost:5432/table"; private static String user = "postgres"; private static String passwd = "toto"; private static Connection connect; public static Connection getInstance(){ if(connect == null){ try { connect = DriverManager.getConnection(url, user, passwd); } catch (SQLException e) { JOptionPane.showMessageDialog(null, e.getMessage(), "Connection Error", JOptionPane.ERROR_MESSAGE); } } return connect; } } And now, in another class I succeeded to print my values but when I attempt to insert a value nothing is happening ... Here's my code : try { Statement state = SQLConnection.getInstance().createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_READ_ONLY); Statement state2 = SQLConnection.getInstance().createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,ResultSet.CONCUR_UPDATABLE); state2.executeUpdate("INSERT INTO table(field1) VALUES (\"Value\")"); // Here's my problem ResultSet res = state.executeQuery("SELECT * FROM plateau");

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• Replace String pattern in Java

  - by Hirantha

  I have the following string "value=\"\\d{4}((((0[1-9])|(1[0-2]))((0[1-9])|([12]\\d)|(3[01]))?)?|(\\-(((0[1-9])|(1[0-2]))(\\-((0[1-9])|([12]\\d)|(3[01])))?)?)?)d{4}" There I want to replace all the occurrences of "{" with NCHAR(0x7B) "}" with NCHAR(0x7D). An the content in-between "{ }" should remain unchanged: Ex: \\d{4} after replacing -> NCHAR(0x7B) 4 NCHAR(0x7D). Is there a way to do this using Regular Expressions in Java?. Anyway, this can be done processing the whole string using string operations.

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• How to implement low pass filter using java

  - by chai

  Hello Everyone, I am trying to implement a low pass filter in Java. My requirement is very simple,I have to eliminate signals beyond a particular frequency (Single dimension). Looks like Butterworth filter would suit my need. Now the important thing is that CPU time should be as low as possible. There would be close to a million sample the filter would have to process and our users don't like waiting too long. Are there any readymade implementation of Butterworth filters which has optimal algorithms for filtering. Regards, Chaitannya

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• Embedded Java Databases for Large Data Sets

  - by ExAmerican

  I would like to port a PHP/MySQL-based client/server application to be a standalone desktop application written in Java. The database has grown to be fairly large, with several tables with hundreds of thousands of rows. I expect these could grow to over a million entries for certain tables. What embedded database would best handle this? HSQLDB and Sqlite seem to be the obvious choices, though I'm guessing there are others out there as well. My main priorities are the ability to perform queries on large amounts of data efficiently (this thread seems to confirm Sqlite can handle this) and the ease with which I can import old data from MySQL (I remember HSQLDB being kind of a pain for that). Note: I am aware that similar questions comparing embedded databases have been posted before (for example here and here) but as my priorities differ somewhat from most applications considering the large data migration I thought it justified a new question.

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• Use of class definitions inside a method in Java

  - by Bragaadeesh

  Hi public class TestClass { public static void main(String[] args) { TestClass t = new TestClass(); } private static void testMethod(){ class TestMethodClass{ int a; int b; int c; } TestMethodClass testMethodClass = new TestMethodClass(); } } I found out that the above piece of code is perfectly legal in Java. I have the following questions. What is the use of ever having a class definition inside a method? Will a class file be generated for TestMethodClass Its hard for me to imagine this concept in an Object Oriented manner. Having a class definition inside a behavior. Probably can someone tell me with equivalent real world examples. Thanks

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• Java : VolatileImage slower than BufferedImage.

  - by Norswap

  I'm making a game in java and in used BufferedImages to render content to the screen. I had performance issues on low end machines where the game is supposed to run, so I switched to VolatileImage which are normally faster. Except they actually slow the whole thing down. The images are created with GraphicsConfiguration.createCompatibleVolatileImage(...) and are drawn to the screen with Graphics.drawImage(...) (follow link to see which one specifically). They are drawn upon a Canvas using double buffering. Does someone has an idea of what is going wrong here ?

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• Web Development In Java Using Netbeans

  - by GigaPr

  Hi I am trying to implement a web application(university project) in java using the following Frameworks Spring Dependency Injection Spring AOP (Logging and Transaction Management) Spring DAO JDBC or HIBERNATE Spring MVC Log4J I create a new Web Application in Netbeans and it gives me a bunch of Files and folders by default. Could anyone explain me what are the files ? Where shall i put the code for the data access layer and business Logic? Or where can i found a basic tutorial to get started(with data access layer, business layer and possibly code example)? Thanks

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