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  • Question About Eclipse Java Debugger Conditional Breakpoints Inefficiency

    - by Personman
    I just set a conditional breakpoint in Eclipse's debugger with a mildly inefficient condition by breakpoint standards - checking whether a HashMap's value list (8 elements) contains Double.NaN. This resulted in an extremely noticeable slowdown in performance - after about five minutes, I gave up. Then I copy pasted the condition into an if statement at the exact same line, put a noop in the if, and set a normal breakpoint there. That breakpoint was reached in the expected 20-30 seconds. Is there something special that conditional breakpoints do that is different from this, or is Eclipse's implementation just kinda stupid? It seems like they could fairly easily just do exactly the same thing behind the scenes.

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  • Need Java Swing equivalent of "scrollIntoView" from Browser DOM

    - by bgould
    I have a JPanel with several levels of child components, also with a JScrollPane. I'm placing a focus listener on some of the child components to add some behavior to those components, but I would also like to have that component scroll into the JPanel's viewport when focus is gained. My question is, does anyone have a general purpose function to do this, similar to the browser DOM function "scrollIntoView"? I've tried muddling through this with various inputs to JComponent.scrollRectToVisible but I guess I haven't figured out the magic word. Thanks in advance.

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  • Trying to get focus onto JTextPane after doubleclicking on JList element (Java)

    - by Alex Cheng
    Hi all. Problem: I have the following JList which I add to the textPane, and show it upon the caret moving. However, after double clicking on the Jlist element, the text gets inserted, but the caret is not appearing on the JTextPane. This is the following code: listForSuggestion = new JList(str.toArray()); listForSuggestion.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); listForSuggestion.setSelectedIndex(0); listForSuggestion.setVisibleRowCount(visibleRowCount); listScrollPane = new JScrollPane(listForSuggestion); MouseListener mouseListener = new MouseAdapter() { @Override public void mouseClicked(MouseEvent mouseEvent) { JList theList = (JList) mouseEvent.getSource(); if (mouseEvent.getClickCount() == 2) { int index = theList.locationToIndex(mouseEvent.getPoint()); if (index >= 0) { Object o = theList.getModel().getElementAt(index); //System.out.println("Double-clicked on: " + o.toString()); //Set the double clicked text to appear on textPane String completion = o.toString(); int num= textPane.getCaretPosition(); textPane.select(num, num); textPane.replaceSelection(completion); textPane.setCaretPosition(num + completion.length()); int pos = textPane.getSelectionEnd(); textPane.select(pos, pos); textPane.replaceSelection(""); textPane.setCaretPosition(pos); textPane.moveCaretPosition(pos); } } theList.clearSelection(); Any idea on how to "de-focus" the selection on the Jlist, or make the caret appear on the JTextPane after the text insertion? I'll elaborate more if this is not clear enough. Please help, thanks!

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  • Dynamically assembling SQL queries in Java

    - by kd
    What is the best way to assemble an SQL query with join conditions dynamically? I don't want to hard code the query for each different condition on a webpage or a set of webpages. Is it even feasible? I got as far as being able to assemble simple queries but i got stumped when i needed to insert join conditions, i.e. how to figure out dependencies for joins etc.

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  • Java Disabled JLabel Reports Mouse Clicked

    - by ikurtz
    colLabels[i].addMouseListener(new MyAdapter()); private class MyAdapter extends MouseAdapter { @Override public void mouseClicked(MouseEvent event) { ColJLabel colJLabel = (ColJLabel)event.getComponent(); System.out.println(colJLabel.ColID); setColumnHeader(false); } } colLabels[i].setEnabled(flag); The situation is this: Mouse clicks are trapped correctly but when i have the JLabel (ColJLabel) control disabled it still reports mouse clicks. How can I make so that mouse clicks are only reported when the control is enabled? Thanks.

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  • Using java abstract class

    - by user969131
    In my UI project, I have few screens that share the same header style only the text is specific to the screens. What will be a good way to implement this? Have the super class create all the header component and open the components to the sub class, the sub class will access to component's setText method to update the text? or Have abstract method in super class to create the components, sub class will implement these methods to create the component. Hope it make sense..

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  • java table question

    - by kate
    hello i have a issue and i want your help i have a table which is called citylink[10][2] and i want to make a check before i move on in my code if it's full to continue if it's not to break!!i know that i should use an if loop but i don't know what to put inside it!!

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  • Java: How to make this Serializable?

    - by Hasslarn
    I dont know that much about Serializable, but i need this class to be. How to achieve it? package helpers; public class XY implements Comparable<XY> { public int x; public int y; public XY (int x, int y) { this.x = x; this.y = y; } public int compareTo( XY other ) { String compare1 = this.x + "-" + this.y; String compare2 = other.x + "-" + other.y; return compare1.compareTo( compare2 ); } public String toString() { return this.x + "-" + this.y; } } As of now i cant send it as an object with outputstream..I´ve tried just to implement Serializable but it doesnt do the trick!

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  • Reverse a given sentence in java

    - by giri
    This was the question asked me in amazon interview. I could not solve the problem properly, Write a program to reverse a given sentence like "This is interview question" the output must be "question interview is this".Can any tell me how to get this done? Thanks in advance

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  • Read text file in java

    - by user326091
    Hi, I have a text file. I would like to retrieve the content from one line to another line. For example, the file may be 200K lines. I want to read the content from line 78 to line 2735. Since the file may be very large, I do not want to read the whole content into the memory. thanks Frank

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  • Bizzare Java invalid Assignment Operator Error

    - by Kay
    public class MaxHeap<T extends Comparable<T>> implements Heap<T>{ private T[] heap; private int lastIndex; private static final int defaultInitialCapacity = 25; public void add(T newItem) throws HeapException{ if (lastIndex < Max_Heap){ heap[lastIndex] = newItem; int place = lastIndex; int parent = (place – 1)/2; //ERROR HERE********** while ( (parent >=0) && (heap[place].compareTo(heap[parent])>0)){ T temp = heap[place]; heap[place] = heap[parent]; heap[parent] = temp; place = parent; parent = (place-1)/2; }else { throw new HeapException(“HeapException: Heap full”); } } } Eclipse complains that there is a: "Syntax error on token "Invalid Character", invalid AssignmentOperator" With the red line beneath the '(place-1)' There shouldn't be an error at all since it's just straight-forward arithmetic. Or is it not that simple?

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  • can this keyword be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • can the keyword 'this' be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • Can you help with regular expressions in Java?

    - by Matt
    I have a bunch of strings which may of may not have random symbols and numbers in them. Some examples are: contains(reserved[j])){ close(); i++){ letters[20]=word I want to find any character that is NOT a letter, and replace it with a white space, so the above examples look like: contains reserved j close i letters word What is the best way to do this?

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  • Java Swing UI Changing Method

    - by vigilant
    I would like to use Swing to program a simple learning game. I am wondering what would be best way to switch between UI screens. For example, I would have a screen for the Main Menu, and then when the user presses a button on that screen, I would swap out the whole screen for a completely different one. Then, arbitrary screens can be swapped in at any moment, and all of their event handlers would be reactivated while the inactive screen's event handlers will be deactivated. What type of Swing component/control would I use for each of the 'screens'. Is this even doable?

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  • converting a UTC time to a local time zone in Java

    - by aloo
    I know this subject has been beaten to death but after searching for a few hours to this problem I had to ask. My Problem: do calculations on dates on a server based on the current time zone of a client app (iphone). The client app tells the server, in seconds, how far away its time zone is away from GMT. I would like to then use this information to do computation on dates in the server. The dates on the server are all stored as UTC time. So I would like to get the HOUR of a UTC Date object after it has been converted to this local time zone. My current attempt: int hours = (int) Math.floor(secondsFromGMT / (60.0 * 60.0)); int mins = (int) Math.floor((secondsFromGMT - (hours * 60.0 * 60.0)) / 60.0); String sign = hours > 0 ? "+" : "-"; Calendar now = Calendar.getInstance(); TimeZone t = TimeZone.getTimeZone("GMT" + sign + hours + ":" + mins); now.setTimeZone(t); now.setTime(someDateTimeObject); int hourOfDay = now.get(Calendar.HOUR_OF_DAY); The variables hour and mins represent the hour and mins the local time zone is away from GMT. After debugging this code - the variables hour, mins and sign are correct. The problem is hourOfDay does not return the correct hour - it is returning the hour as of UTC time and not local time. Ideas?

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  • What is a good "Error Checking" Pattern (Java)?

    - by Jack
    I'll explain what I mean by input error checking. Say you have a function doSomething(x). If the function completes successfully doSomething does something and returns nothing. However, if there are errors I'd like to be notified. That is what I mean by error checking. I'm looking for, in general, the best way to check for errors. I've thought of the following solutions, each with a potential problem. Flag error checking. If doSomething(x) completes successfully return null. Otherwise, it returns a boolean or an error string. Problem: Side effects. Throwing an exception. Throw an exception if doSomething(x) encounters an error. Problem: If you are performing error checking for parameters only, throwing an IllegalArgumentExceptionseems inappropriate. Validating input prior to function call. If the error checking is only meant for the parameters of the function, then you can call a validator function before calling the doSomething(x) function. Problem: What if a client of the class forgets to call the validator function before calling doSomething(x)? I often encounter this problem and any help or a point in the right direction would be much appreciated.

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  • java.lang.NumberFormatException: unable to parse '' as integer one more time

    - by Quzziy
    I will take two numbers from user, but this number from EditText must be converted to int. I think it should be working, but I still have problem with compilation code in Android Studio. CatLog show error in line with: int wiek = Integer.parseInt(wiekEditText.getText().toString()); Below is my full Android code: public class MyActivity extends ActionBarActivity { int Wynik; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_my); int Tmax, RT; EditText wiekEditText = (EditText) findViewById(R.id.inWiek); EditText tspoczEditText = (EditText) findViewById(R.id.inTspocz); int wiek = Integer.parseInt(wiekEditText.getText().toString()); int tspocz = Integer.parseInt(tspoczEditText.getText().toString()); Tmax = 220 - wiek; RT = Tmax - tspocz; Wynik = 70*RT/100 + tspocz; final EditText tempWiekEdit = wiekEditText; TabHost tabHost = (TabHost) findViewById(R.id.tabHost); //Do TabHost'a z layoutu tabHost.setup(); TabHost.TabSpec tabSpec = tabHost.newTabSpec("Calc"); tabSpec.setContent(R.id.Calc); tabSpec.setIndicator("Calc"); tabHost.addTab(tabSpec); tabSpec = tabHost.newTabSpec("Hints"); tabSpec.setContent(R.id.Hints); tabSpec.setIndicator("Hints"); tabHost.addTab(tabSpec); final Button Btn = (Button) findViewById(R.id.Btn); Btn.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { Toast.makeText(getApplicationContext(),"blablabla"+ "Wynik",Toast.LENGTH_SHORT).show(); } }); wiekEditText.addTextChangedListener(new TextWatcher() { @Override public void beforeTextChanged(CharSequence s, int start, int count, int after) { } @Override public void onTextChanged(CharSequence s, int start, int before, int count) { Btn.setEnabled(!(tempWiekEdit.getText().toString().trim().isEmpty())); } @Override public void afterTextChanged(Editable s) { } }); } @Override public boolean onCreateOptionsMenu(Menu menu) { // Inflate the menu; this adds items to the action bar if it is present. getMenuInflater().inflate(R.menu.my, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { // Handle action bar item clicks here. The action bar will // automatically handle clicks on the Home/Up button, so long // as you specify a parent activity in AndroidManifest.xml. int id = item.getItemId(); if (id == R.id.action_settings) { return true; } return super.onOptionsItemSelected(item); } }

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  • Set the amount of rows JList show (Java)

    - by Alex Cheng
    Hi all. Problem: I have a method that creates a list from the parsed ArrayList. I manage to show the list in the GUI, without scrollbar. However, I am having problem setting it to show only the size of ArrayList. Meaning, say if the size is 6, there should only be 6 rows in the shown List. Below is the code that I am using. I tried setting the visibleRowCount as below but it does not work. I tried printing out the result and it shows that the change is made. private void createSuggestionList(ArrayList<String> str) { int visibleRowCount = str.size(); System.out.println("visibleRowCount " + visibleRowCount); listForSuggestion = new JList(str.toArray()); listForSuggestion.setSelectionMode(ListSelectionModel.SINGLE_SELECTION); listForSuggestion.setSelectedIndex(0); listForSuggestion.setVisibleRowCount(visibleRowCount); System.out.println(listForSuggestion.getVisibleRowCount()); listScrollPane = new JScrollPane(listForSuggestion); MouseListener mouseListener = new MouseAdapter() { @Override public void mouseClicked(MouseEvent mouseEvent) { JList theList = (JList) mouseEvent.getSource(); if (mouseEvent.getClickCount() == 2) { int index = theList.locationToIndex(mouseEvent.getPoint()); if (index >= 0) { Object o = theList.getModel().getElementAt(index); System.out.println("Double-clicked on: " + o.toString()); } } } }; listForSuggestion.addMouseListener(mouseListener); textPane.add(listScrollPane); repaint(); } To summarize: I want the JList to show as many rows as the size of the parsed ArrayList, without a scrollbar. Any ideas? Please help. Thanks. Please let me know if a picture of the problem is needed in case I did not phrase my question correctly.

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  • Java Null Pointer Exception :-(

    - by John-Michael Reed
    I've got a Null Pointer Exception in my main that just won't go away and I'm totally out of ideas. The error is on the line "Board[x][y].color = 2;" in which Board is a public, static array of piece objects that contain instance variables like the one "color" that is being set to 2 in the above statement. Pieces is not static - that is there are many different copies of pieces, each with its own data, but only one board. The array has been initialized and defined as both public Piece[][] Board = new Piece[8][8] and public static Piece[][] Board = new Piece[8][8], but no matter how I mess around with it (getting rid of static, putting the variable in another object, etc.), I can't seem to get the error to go away. Help?

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