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  • Java Variable Initialization

    - by Samuel Brainard
    Here's a piece of code I wrote. public class cube { private int length; private int breadth; private int height; private int volume; private int density; private int weight; public cube(int l,int b,int h, int d) { length=l; breadth=b; height=h; density=d; } public void volmeShow(){ volume=length*breadth*height; System.out.println("The Volume of the cube is "+this.volume); So if I implement the above cube class like this, public class cubeApp { public static void main(String[] args){ cube mycube = new cube(5,6,9,2); mycube.volumeShow(); I get an output that tells me Volume is 270. But I get an output that says Volume is 0 if I define the volume variable like this: public class cube { private int length; private int breadth; private int height; private int volume=length*breadth*height; private int density; private int weight; public cube(int l,int b,int h, int d) { length=l; breadth=b; height=h; density=d; } public void volmeShow(){ System.out.println("The Volume of the cube is "+this.volume); Can somebody please explain why this is happening? Thanks, Samuel.

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  • how to convert BigInteger to String in java

    - by Bipul
    i converted a string to BigInteger as follows: Scanner sc=new Scanner(System.in); System.out.println("enter the message"); String msg=sc.next(); byte[] bytemsg=msg.getBytes(); BigInteger m=new BigInteger(bytemsg); now i want my string back.i m using m.toString() method but not getting desired result. why??? what is bug in it and what is its remedy.

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  • Java Swing Forms Catching Data

    - by RhigoHR
    Hi everybody, I have a form in swing with a lot of textfields receiving data, then, the idea is when a click on a botton, the app catch all the data from the textfields. Do you know a good practice for this?, or is it necessary to catch textfield by textfield to get the data?.. Thx for your time.

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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 beginner- in which folder should I place a "database.properties" file

    - by Arvind
    I read some tutorials on how to read data from a database.properties file- which basically stored key-value pairs. What i want to know is, in which folder should I place this file? Is it in the root (ie "src") or within a package... And how do I access this file, if it is placed in "src"- my code will be within a package (and the package's directory will be under src)- so how do I access the properties file, which is in "src", from a class within a package?

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  • Reflection for Class of generic parameter in Java?

    - by hatboysam
    Imagine the following scenario: class MyClass extends OtherClass<String>{ String myName; //Whatever } class OtherClass<T> { T myfield; } And I am analyzing MyClass using reflection specifically (MyClass.class).getDeclaredFields(), in this case I will get the following fields (and Types, using getType() of the Field): myName --> String myField --> T I want to get the actual Type for T, which is known at runtime due to the explicit "String" in the extends notation, how do I go about getting the non-genetic type of myField?

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  • Using Java method to display HTML code

    - by javArc
    Hey folks, ok so this is my problem, I need to display HTML code in a jsp, which wouldn't be a problem, except a requirement for this project is that we place all the code in a public class file and have seperate methods for each chunk(header, sidebar footer, etc). Now here's where i'm confused: "Your method should take the PrintWriter as a parameter to print out each line of HTML, and should have a return type of void" What does that mean? How do I pass the PrintWriter into a method? Does this make sense to anyone?

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  • Negative look ahead java

    - by venu
    I need an expression to capture a string like this "A"[A string that is NOT atleast 5 and atmost 6 digits]"B", In other words capture anything that is NOT the following A[0-9][0-9][0-9][0-9][0-9]B A[0-9][0-9][0-9][0-9][0-9][0-9]B I have tried the negative look ahead regex = "a((?![0-9]{5,6}).)*d" ; But it fails to capture all scenarios. Please help venu

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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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  • 2 bucks for !! java basic question

    - by Max
    How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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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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  • Simple stream read/write question in java

    - by Marius
    Hi, I'm trying to upload a file via URLConnection, but i need to read/write it as a binary file without any encoding changes. So i've tried to read byte[] array from FileInputStream, but now i have an issue. The PrintWriter object i use for outputing to the server does not allow me to do writer.write(content) (where content is of type byte[]). How can i fix this? Or is there another way to quickly copy binary data from a FileInputStream to a PrintWriter? Thank you

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  • Using enums in Java across multiple classes

    - by Richard Mar.
    I have the following class: public class Card { public enum Suit { SPACES, HEARTS, DIAMONDS, CLUBS }; public Card(Suit nsuit, int nrank) { suit = nsuit; rank = nrank; } private Suit suit; private int rank; } I want to instantiate it in another class, but that class doesn't understand the Suit enum. Where should I put the enum to make it publicly visible?

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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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  • Deferred printing in Java

    - by Bober02
    I have a specific issue with general console printing and I was wondering whether anyone has a solution for it. I am trying to print a dataTable which would look like sth like this: Table ---------------------- Name |Surname | ---------------------- Mike |Mikhailowish| Rafaello|Mirena | and so on. In order to print the border of the bar I need to know what the maximum length of each column value is. I don't want to go through the whole database to find that out and then again to print it. I would rather like to do sth like: System.out.printLater(s); //herejust leave a pointer to a StringBuilder you will build ... s.append("--------"); ... System.out.printAllDeferred(); I understand the above is probably in 99.99999% chances impossible, but perhaps you guys have a clever way of achieving the above?

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  • java switch case question

    - by hkvega
    public String sizeOfSupermarket() { String size; switch (this.numberOfProducts) { case (this.numberOfProducts > 5000): size = "Large"; break; case (this.numberOfProducts > 2000 && this.numberOfProducts < 5000): size = "Medium"; break; case (this.numberOfProducts < 2000): size = "Small"; break; } return size; } the above is wrong, how to write the compare statement in case statement?

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  • Relational Database arrays (H2, Java)

    - by Daddy Warbox
    I seem to have two options on how to implement arrays, and I want to know which I should go with: Use the ARRAY data type and (from what I understand) effectively serialize data objects into the database (which in my case are just wrapped primitive types; don't know of another way to make this work). Use a separate table and map with foreign keys for each array item. If you have experience with this (especially with H2), which would you recommend?

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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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  • 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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  • How do I make java wait for boolean to run funciton

    - by TWeeKeD
    I'm sure this is pretty simple but I can't figure out and it sucks I'm up on suck on (what should be) an easy step. ok. I have a method that runs one function that give a response. this method actually handles the uploading of the file so o it takes a second to give a response. I need this response in the following method. sendPicMsg needs to complete and then forward it's response to sendMessage. Please help. b1.setOnClickListener(new View.OnClickListener() { public void onClick(View v) { if(!uploadMsgPic.equalsIgnoreCase("")){ Log.v("response","Pic in storage"); sendPicMsg(); sendMessage(); }else{ sendMessage(); } 1st Method public void sendPicMsg(){ Log.v("response", "sendPicMsg Loaded"); if(!uploadMsgPic.equalsIgnoreCase("")){ final SharedPreferences preferences = this.getActivity().getSharedPreferences("MyPreferences", getActivity().MODE_PRIVATE); AsyncHttpClient client3 = new AsyncHttpClient(); RequestParams params3 = new RequestParams(); File file = new File(uploadMsgPic); try { File f = new File(uploadMsgPic.replace(".", "1.")); f.createNewFile(); //Convert bitmap to byte array Bitmap bitmap = decodeFile(file,400); ByteArrayOutputStream bos = new ByteArrayOutputStream(); bitmap.compress(CompressFormat.PNG, 0 /*ignored for PNG*/, bos); byte[] bitmapdata = bos.toByteArray(); //write the bytes in file FileOutputStream fos = new FileOutputStream(f); fos.write(bitmapdata); params3.put("file", f); } catch (FileNotFoundException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } params3.put("email", preferences.getString("loggedin_user", "")); params3.put("webversion", "1"); client3.post("http://peekatu.com/apiweb/msgPic_upload.php",params3, new AsyncHttpResponseHandler() { @Override public void onSuccess(String response) { Log.v("response", "Upload Complete"); refreshChat(); //responseString = response; Log.v("response","msgPic has been uploaded"+response); //parseChatMessages(response); response=picurl; uploadMsgPic = ""; if(picurl!=null){ Log.v("response","picurl is set"); } if(picurl==null){ Log.v("response", "picurl no ready"); }; } }); sendMessage(); } } 2nd Method public void sendMessage(){ final SharedPreferences preferences = this.getActivity().getSharedPreferences("MyPreferences", getActivity().MODE_PRIVATE); if(preferences.getString("Username", "").length()<=0){ editText1.setText(""); Toast.makeText(this.getActivity(), "Please Login to send messages.", 2); return; } AsyncHttpClient client = new AsyncHttpClient(); RequestParams params = new RequestParams(); if(type.equalsIgnoreCase("3")){ params.put("toid",user); params.put("action", "sendprivate"); }else{ params.put("room", preferences.getString("selected_room", "Adult Lobby")); params.put("action", "insert"); } Log.v("response", "Sending message "+editText1.getText().toString()); params.put("message",editText1.getText().toString() ); params.put("media", picurl); params.put("email", preferences.getString("loggedin_user", "")); params.put("webversion", "1"); client.post("http://peekatu.com/apiweb/messagetest.php",params, new AsyncHttpResponseHandler() { @Override public void onSuccess(String response) { refreshChat(); //responseString = response; Log.v("response", response); //parseChatMessages(response); if(picurl!=null) Log.v("response", picurl); } }); editText1.setText(""); lv.setSelection(adapter.getCount() - 1); }

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  • Java : Singleton class instances in a Web based Application

    - by Preethi Jain
    I have this Singleton class inside a Web Application . public class MyDAO { private static MyDAO instance; private MyDAO() { } public static MyDAO getInstance() { if (instance == null) { instance = new MyDAO(); } return instance; } I will access it this way public void get_Data() { MyDAO dao = MyDAO.getInstance(); } How many Objects of MyDAO class will be created if there are 3 Users accessing the Application ?? Will there be one instance of MyDAO per User ??

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