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• My Java regex isn't capturing the group

  - by Geo

  I'm trying to match the username with a regex. Please don't suggest a split. USERNAME=geo Here's my code: String input = "USERNAME=geo"; Pattern pat = Pattern.compile("USERNAME=(\\w+)"); Matcher mat = pat.matcher(input); if(mat.find()) { System.out.println(mat.group()); } why doesn't it find geo in the group? I noticed that if I use the .group(1), it finds the username. However the group method contains USERNAME=geo. Why?

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• Error in create back up in mysql through java program

  - by Arivu2020

  Runtime.getRuntime().exec("C:\mysql\bin\mysqldump -u root -pmypassword Databasename -r C:/backup.sql"); I am using this code to create back up from my sql. but It creates the empty file in the path.Because it is waiting in the command prompt to get the password. How can i give password to it Using command prompt directly when i press enter after typing, it asks password.After giving password,It creates the backup.Give me any solution for this Thanks in advance

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• Java Swing - Adding a row # column to a JTable

  - by llm

  I have data from a database loaded into a JTable through a custom table model. I want to have a column (should be the first column) which simply shows the display row number (i.e. it is not tied to any data (or sorting) but is simply the row number on the screen starting at 1). These "column headers" should be grayed out like the row headers. Any idea how to do this? Thanks

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• Swapping switch-case in extra fle/data structure (Java)

  - by poeschlorn

  Hi guys, it may be a nooby question, but I've never needed it before: I have several strings and I want to compare them to given ones... At first glance it would lead to a switch/case construction in what every available entry is checked. Is there a more elegant way to swap those strings as key/value datas? greets, poeschlorn

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• Java Object Array item to String Array

  - by user341264

  Say I have the following: Class myclass { public string stra ="", strb = "" myclass(String a, String b){stra=a;strb=b} } //then in the app I want to do: myclass myclassinst1 = new myclass("blah","xxxx"); myclass myclassinst2 = new myclass("blah2","yyyy"); myclass myclassinst3 = new myclass("blah3","zzzz"); list <myclass> mylist = new ArrayList<myclass>(); mylist.add(myclassinst1 ); mylist.add(myclassinst2 ); mylist.add(myclassinst3 ); //How would I then convert that to a String[] Array of all the stra elements without using a loop. //eg: String[] strarr_a = mylist.toarray(myclass.stra); String[] strarr_b = mylist.toarray(myclass.strb); //instead of having to do String[] strarr_a = new String[mylist.size()]; String[] strarr_b = new String[mylist.size()]; for (int i=0;i<mylist.size();i++) { strarr_a[i] = mylist.get(i).stra; strarr_b[i] = mylist.get(i).strb; }

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• java oracle cusor is closed where cursor is not return to jdbc

  - by optimus

  I am executing a stored procedure which has 2 cusors within the stored procedure. The 1st cursor which is not return to the jdbc as a resultset is closed within the stored procedure. The 2nd cursor which returns the resultset to the jdbc is not closed within the stored procedure. Upon executing I encounter cursor is closed exception which is puzzling. Since the ResultSet will close all underlying cursor upon invoking the close() method

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• PasswordFiled char[] to String in Java connection MySql?

  - by user1819551

  This is a jFrame to connect to the database and this is in the button connect. My issue is in the passwordField NetBeans make me do a char[], but my .getConnection not let me insert the char[] ERROR: "no suitable method found for getConnection(String,String,char[])". So I will change to String right? So when I change and run the jFrame said access denied. when I start doing the System.out.println(l) " Give me the right answer" Like this: "Alex". But when I do the System.out.println(password) "Give me the Array spaces and not the value" Like this: jdbc:mysql://localhost/home inventory root [C@5be5ab68 <--- Array space . What I doing wrong? try { Class.forName("org.gjt.mm.mysql.Driver"); //Load the driver String host = "jdbc:mysql://"+tServerHost.getText()+"/"+tSchema.getText(); String uName = tUsername.getText(); char[] l = pPassword.getPassword(); System.out.println(l); String password= l.toString(); System.out.println(host+uName+l); con = DriverManager.getConnection(host, uName, password); System.out.println(host+uName+password); } catch (SQLException | ClassNotFoundException ex) { JOptionPane.showMessageDialog(this, ex.getMessage()); } }

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• Hiding "Print to file" in a Java print dialog

  - by Carl Smotricz

  I'm maintaining this Swing app that has a "print" option. Users need to be kept from interacting in any way with the underlying file system, but the print dialog offers "print to file" as one printer, and that of course allows selecting a directory and file from the file system. Is there a painless way to override/modify the print dialog to hide the "to file" printer from this dialog? I understand the API will let me do this piecemeal but I'd rather not have to re-create most of the dialog GUI and functionality to do this.

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• directory traversal in Java using different regular and enhanced for loops

  - by user3245621

  I have this code to print out all directories and files. I tried to use recursive method call in for loop. With enhanced for loop, the code prints out all the directories and files correctly. But with regular for loop, the code does not work. I am puzzled by the difference between regular and enhanced for loops. public class FileCopy { private File[] childFiles = null; public static void main(String[] args) { FileCopy fileCopy = new FileCopy(); File srcFile = new File("c:\\temp"); fileCopy.copyTree(srcFile); } public void copyTree(File file){ if(file.isDirectory()){ System.out.println(file + " is a directory. "); childFiles = file.listFiles(); /*for(int j=0; j<childFiles.length; j++){ copyTree(childFiles[j]); } This part is not working*/ for(File a: childFiles){ copyTree(a); } return; } else{ System.out.println(file + " is a file. "); return; } } }

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• Waiting for a subset of threads in a Java ThreadPool

  - by David Semeria

  Let's say I have a thread pool containing X items, and a given task employs Y of these items (where Y is much smaller than X). I want to wait for all of the threads of a given task (Y items) to finish, not the entire thread pool. If the thread pool's execute() method returned a reference to the employed thread I could simply join() to each of these Y threads, but it doesn't. Does anyone know of an elegant way to accomplish this? Thanks.

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• best way to create UI java apps ?

  - by fwfwfw

  I've come across Netbeans but is there any tools out there that lets you build things event driven ? I'm looking for a feature like being able to drag and drop UI components, and add methods to buttons directly by double clicking it (kinda like visualbasic) and viewing the source.

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• Hash Tables - Java

  - by Antony

  Am about to do a homework, and i need to store quite a lot of information (Dictionary) in a data structure of my choice. I heard people in my classroom saying hash-tables are the way to go. How come?

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• Strange behavior when overloading methods in Java

  - by Sep

  I came across this weird (in my opinion) behavior today. Take this simple Test class: public class Test { public static void main(String[] args) { Test t = new Test(); t.run(); } private void run() { List<Object> list = new ArrayList<Object>(); list.add(new Object()); list.add(new Object()); method(list); } public void method(Object o) { System.out.println("Object"); } public void method(List<Object> o) { System.out.println("List of Objects"); } } It behaves the way you expect, printing "List of Objects". But if you change the following three lines: List<String> list = new ArrayList<String>(); list.add(""); list.add(""); you will get "Object" instead. I tried this a few other ways and got the same result. Is this a bug or is it a normal behavior? And if it is normal, can someone explain why? Thanks.

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• Java LinkedList iterator being exhausted prematurely

  - by Sujeet

  I am using LinkedList and retrieving an Iterator object by using list.iterator(). After that, I am checking it.hasNext(), real issue is while checking it.hasNext(), sometimes it returns false. I need help why this is happening, though I have elements in the list. Some code: public synchronized void check(Object obj) throws Exception { Iterator itr = list.iterator(); while(itr.hasNext()) { //This Line I get false.. though i have list size is 1 Item p = (Item)itr.next(); if(p.getId() == null) {continue;} if(p.getId().getElemntId() == obj.getId() || obj.getId() == 0 ) { p.setResponse(obj); notifyAll(); return; } } Log.Error("validate failed obj.getId="+obj.getId()+" **list.size="+list.size()*This shows 1*); throw new Exception("InvalidData"); }

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• Confusion in multi dimensional array in Java

  - by Alvin

  Hello, I'm not able to understand the following multi-dimensional code. Could someone please clarify me? int[][] myJaggedArr = new int [][] { new int[] {1,3,5,7,9}, new int[] {0,2,4,6}, new int[] {11,22} }; May I know how it is different from the following code? int[][] myArr = new int [][] { {1,3,5,7,9}, {0,2,4,6}, {11,22} };

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• Regular expression one or more times JAVA

  - by user1381564

  Hi i am trying to match a string against a pattern this is the possible string signal CS, NS, dl: stateType := writeOrRead0; signal CS, pS : stateType := writeOrRead0; signal dS : stateType := writeOrRead0; i am only concerned with the pattern as far as the first colon. but the number of signals define can be more than one it could be three or four even this is the regular expression i have ^signal\\s*(\\w+),*\\s*(\\w+)\\s*: it will pick up the second two signal but and for the second one it picks up CS and pS and but the d and S in the next signal when i use matcher.group() come up seperately Can anyone give me an expression that will pick up all signal names whether there is one two three or more?

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• How to build our own java custom layout

  - by nguyendat

  Please help me how to creat own custom layout, container, component, layout manager... Example: Containers and Layout Managers Create a window frame. Nest panels within a frame for better layout control. Create and display buttons in a panel. List two component attributes that are controlled by a layout manager. Set the layout manager for a container. Place components in a panel using BorderLayout, GridLayout, and FlowLayout. Name one advantage of each of the layout managers. Create panels with titles. i was search on google but can't find any that match my requirement Thanks for your help

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• URL Routing in Java

  - by Jack

  Coming from other web frameworks, I'm used to being able to map parts of a URL to method parameters. I know that web.xml provides a way to map an entire URL to a Servlet but is there a way to get more features out of this, such as mapping pieces of the URL to method parameters?

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• ArithmeticException Java?

  - by KP65

  Can anyone help me find where the execption is? I can't seem to find the problem.. public void fieldChanged(Field f, int context){ //if the submit button is clicked try{ stopTime = System.currentTimeMillis(); timeTaken = stopTime - startTime; timeInSecs = ((timeTaken/1000)); speed = 45/timeInSecs; Dialog.alert("Speed of Delivery: " + speed + "mph"); } catch(ArithmeticException e){ Dialog.alert("error " + speed); e.printStackTrace(); } } startTime variable is a global variable..

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• Java : Count even values in a Binary Search Tree recursively

  - by user307682

  Hi, I need to find out how many even values are contained in a binary tree. this is my code. private int countEven(BSTNode root){ if ((root == null)|| (root.value%2==1)) return 0; return 1+ countEven(root.left) + countEven(root.right); } this i just coded as i do not have a way to test this out. I'm not able to test it out at the moment but need an answer so badly. any help is deeply appreciated.

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• Java : Using parent class method to access child class variable

  - by Jayant

  I have the following scenario : public class A { private int x = 5; public void print() { System.out.println(x); } } public class B extends A { private int x = 10; /*public void print() { System.out.println(x); }*/ public static void main(String[] args) { B b = new B(); b.print(); } } On executing the code, the output is : 5. How to access the child class(B's) variable(x) via the parent class method? Could this be done without overriding the print() method (i.e. uncommenting it in B)? [This is important because on overriding we will have to rewrite the whole code for the print() method again]

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• What is the eclipse java declaration shortcut ?

  - by Felipe

  There´s any eclipse shortcut to stance a new object ? For example. I would like to type: Object zzz = and it would complete for me this way: Object zzz = new Object(); with void parameter of course. I will wait answers.. thank you people.

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• Rotation in a Vector2d class in Java

  - by wanstein

  I've been working on this for one hour, just can't get it. I have a Vector2d class: public class Vector2d { public double x = 0.0; public double y = 0.0; .... } This vector class has a rotate() method which is causing me trouble. The first snippet seems to make the x and y values smaller and smaller. The second one works just fine! Am I missing something simple here? public void rotate(double n) { this.x = (this.x * Math.cos(n)) - (this.y * Math.sin(n)); this.y = (this.x * Math.sin(n)) + (this.y * Math.cos(n)); } This works: public void rotate(double n) { rx = (this.x * Math.cos(n)) - (this.y * Math.sin(n)); ry = (this.x * Math.sin(n)) + (this.y * Math.cos(n)); x = rx; y = ry; } I just can't spot any difference there

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• Java code compression and decompression of a string

  - by user1822710

  I am having a problem figuring how to check a string for the same characters in a row then count that same character in a row then printing it out then giving the location of the last occorance of that character count then printing it out then moving to the next character in the string that is different then the previous character and the program is case sensitive. So the input could be: aaaaAAAbbbddccc How would I compress this string to: a4A3b3d2c3 ? and then decompress it?

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• Generics Java and Shadowing of type parameters

  - by rubixibuc

  This code seems to work fine class Rule<T> { public <T>Rule(T t) { } public <T> void Foo(T t) { } } Does the method type parameter shadow the class type parameter? Also when you create an object does it use the type parameter of the class? example Rule<String> r = new Rule<String>(); Does this normally apply to the type parameter of the class, in the situation where they do not conflict? I mean when only the class has a type parameter, not the constructor, or does this look for a type parameter in the constructor? If they do conflict how does this change? SEE DISCUSSION BELOW if I have a function call x = <Type Parameter>method(); // this is a syntax error even inside the function or class ; I must place a this before it, why is this, and does everything still hold true. Why don't I need to prefix anything for the constructor call. Shouldn't Oracle fix this.

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