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  • Initialize an object in java

    - by harigm
    Is it the right Way we initialise the the object? I have a class Sample I want to initialise the Object in my Sample1 Class After intialisation I dont require to use the object of Sample Class. In that Case Can I initialise that object as new Sample(); instead of Sample s = new Sample(); if I am not going to use s anywhere in my Sample1 Class My question, is this a good practice to do that? will there be any after affects

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  • Constructors from extended class in Java

    - by Crystal
    I'm having some trouble with a hw assignment. In one assignment, we had to create a Person class. Mine was: public class Person { String firstName; String lastName; String telephone; String email; public Person() { firstName = ""; lastName = ""; telephone = ""; email = ""; } public Person(String firstName) { this.firstName = firstName; } public Person(String firstName, String lastName, String telephone, String email) { this.firstName = firstName; this.lastName = lastName; this.telephone = telephone; this.email = email; } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getTelephone() { return telephone; } public void setTelephone(String telephone) { this.telephone = telephone; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } public boolean equals(Object otherObject) { // a quick test to see if the objects are identical if (this == otherObject) { return true; } // must return false if the explicit parameter is null if (otherObject == null) { return false; } if (!(otherObject instanceof Person)) { return false; } Person other = (Person) otherObject; return firstName.equals(other.firstName) && lastName.equals(other.lastName) && telephone.equals(other.telephone) && email.equals(other.email); } public int hashCode() { return 7 * firstName.hashCode() + 11 * lastName.hashCode() + 13 * telephone.hashCode() + 15 * email.hashCode(); } public String toString() { return getClass().getName() + "[firstName = " + firstName + '\n' + "lastName = " + lastName + '\n' + "telephone = " + telephone + '\n' + "email = " + email + "]"; } } Now we have to extend that class and use that class in our constructor. The function protoype is: public CarLoan(Person client, double vehiclePrice, double downPayment, double salesTax, double interestRate, CAR_LOAN_TERMS length) I'm confused on how I use the Person constructor from the superclass. I cannot necessarily do super(client); in my constructor which is what the book did with some primitive types in their example. Not sure what the correct thing to do is... Any thoughts? Thanks!

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  • Java nullPointerException with getter and setters on an object

    - by 12345
    I'm getting a nullPointerException below. Can someone explain why? Thanks! private SpatialPooler spatialPooler; private Region region; private Column column33; public void setUp() { this.spatialPooler = new SpatialPooler(); this.region = new Region(30, 40, 6, 8, 1.0f, 1, 1); this.column33 = this.region.getColumn(3, 3); } public void addActiveColumn(Column activeColumn) { this.activeColumns.add(activeColumn); // nullPointerException here! } public Column getActiveColumn(int x, int y) { for (Column activeColumn : this.activeColumns) { if (activeColumn.getX() == x && activeColumn.getY() == y) { return activeColumn; } } return null; } // in a test class that is in the same package. public void testGetAndAddActiveColumn() { this.spatialPooler.addActiveColumn(this.column33); assertNull(this.spatialPooler.getActiveColumn(3, 3)); this.column33.setActiveState(true); assertEquals(this.column33, this.spatialPooler.getActiveColumn(3, 3)); }

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  • Java: GatheringByteChannel advantages?

    - by Jason S
    I'm wondering when the GatheringByteChannel's write methods (taking in an array of ByteBuffers) have advantages over the "regular" WritableByteChannel write methods. I tried a test where I could use the regular vs. the gathering write method on a FileChannel, with approx 400KB/sec total in ByteBuffers of between 23-27 bytes in length in both cases. Gathering writes used an array of 64. The regular method used up approx 12% of my CPU, and the gathering method used up approx 16% of my CPU (worse than the regular method!) This tells me it's NOT useful to use gathering writes on a FileChannel around this range of operating parameters. Why would this be the case, and when would you ever use GatheringByteChannel? (on network I/O?) Relevant differences here: public void log(Queue<Packet> packets) throws IOException { if (this.gather) { int Nbuf = 64; ByteBuffer[] bbufs = new ByteBuffer[Nbuf]; int i = 0; Packet p; while ((p = packets.poll()) != null) { bbufs[i++] = p.getBuffer(); if (i == Nbuf) { this.fc.write(bbufs); i = 0; } } if (i > 0) { this.fc.write(bbufs, 0, i); } } else { Packet p; while ((p = packets.poll()) != null) { this.fc.write(p.getBuffer()); } } }

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  • Simple Java web application on Tomcat

    - by EugeneP
    If we only need to graphically authorize a user, view a few tables representation (from database), ability to change data in the database visually what tools to use to write such a web application that will run on Tomcat? What framework allows to do that in the most straightforward, easy-to-manage and elegant way?

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  • comlen function in Java

    - by davit-datuashvili
    in c or c++ the function comlen is defined such int comlen(char *p,char *q){ int i=0; while *p && (*p++==*q++) i++; return i; } Is this code equivalent of this function? int comlen(String s,String m){ int i=0; while (i<s.length() && s.charAt(i)==m.charAt(i)){ i++; } return i; }

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  • Need help with java map and javabean

    - by techoverflow
    Hi folks, I have a nested map: Map<Integer, Map<Integer, Double>> areaPrices = new HashMap<Integer, Map<Integer, Double>>(); and this map is populated using the code: while(oResult.next()) { Integer areaCode = new Integer(oResult.getString("AREA_CODE")); Map<Integer, Double> zonePrices = areaPrices.get(areaCode); if(zonePrices==null) { zonePrices = new HashMap<Integer, Double>(); areaPrices.put(areaCode, zonePrices); } Integer zoneCode = new Integer(oResult.getString("ZONE_CODE")); Double value = new Double(oResult.getString("ZONE_VALUE")); zonePrices.put(zoneCode, value); myBean.setZoneValues(areaPrices); } I want to use the value of this Map in another method of the same class. For that I have a bean. How do I populate it on the bean, so that I can get the ZONE_VALUE in this other method In my bean I added one new field as: private Map<Integer, Map<Integer, Double>> zoneValues; with getter and setter as: public Map<Integer, Map<Integer, Double>> getZoneValues() { return zoneValues; } public void setZoneValues(Map<Integer, Map<Integer, Double>> areaPrices) { this.zoneValues = areaPrices; } What I am looking for to do in the other method is something like this: Double value = myBean.get(areaCode).get(zoneCode); How do I make it happen :(

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  • Android java assigning 2d array to 3d array

    - by semajhan
    I'm running into problems trying to assign a 2d array to a 3d array, so I thought i'd ask a question about 3d and 2d arrays. Say I have a masterArray[][][] and wanted to put childArray1[][] and childArray2[][] into it. This is how I have done it and was wondering if that is the correct way of applying it: private int[][][] masterArray; private int[][] childArray1 = { {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 0, 0, 1, 0, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 0, 1, 1, 1, 1, 1, 1, 0, 1}, {1, 0, 1, 1, 1, 1, 0, 1, 0, 1}, {1, 0, 1, 1, 0, 1, 0, 1, 0, 1}, {1, 0, 1, 1, 0, 1, 1, 1, 0, 1}, {1, 0, 1, 1, 1, 1, 1, 1, 0, 1}, {1, 0, 1, 1, 0, 1, 1, 1, 0, 1}, {1, 0, 1, 1, 0, 1, 8, 1, 0, 1}, {1, 0, 7, 1, 1, 1, 0, 1, 0, 1}, {1, 0, 1, 1, 1, 1, 0, 1, 0, 1}, {1, 0, 1, 1, 1, 1, 1, 1, 0, 1}, {1, 0, 0, 0, 0, 0, 0, 9, 0, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1} }; private int[][] childArray2 = { {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {0, 0, 0, 0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 7, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 0, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 0, 0, 0, 1, 1, 1}, {1, 1, 1, 9, 1, 1, 8, 0, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1, 1}, }; Ok, so in my init method I use these some methods to set the child arrays into the master array. What I was curious about was how this exactly works. I assumed the following: masterLevel = new int[MAX_LEVELS][MAP_WIDTH][MAP_HEIGHT]; for (int x = 0; x < MAP_WIDTH; x++) { for (int y = 0; y < MAP_HEIGHT; y++) { masterArray[currentLevel][x][y] = childArray1[x][y]; } } Would that work? In my application things aren't working so I picking out code that I am not 100% sure on.

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  • Java Insert Help...???

    - by El Classico
    I am trying to do an Insert, Update and Delete on a table in MS Access. Everything works fine for a SELECT statement. But when doing the other three operations, I don't seem to get any errors, but the actions are not reflected on to the DB. Please help... THe INSERT statement is as follows: PreparedStatement ps = con.prepareStatement("INSERT INTO Student VALUES (?, ?, ?, ?, ?, ?, ?, ?)"); ps.setInt(1,1); ps.setString(2,"ish"); ps.setInt(3,100); ps.setInt(4,100); ps.setInt(5,100); ps.setInt(6,300); ps.setInt(7,100); ps.setString(8,"A"); ps.executeUpdate(); Also may I know why PreparedStatement is used except for SELECT statement...

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  • how to get the PageFormat from a Java.awt.print.PrinterJob

    - by Alex
    Hi, I'm trying to use the PageFormat information to modify my javax.swing based printout prior to printing it. I am stumped as to how I can get the PageFormat from the PrintJob (which is obtained using getPrinterJob() and printDialog()). I know there is the getPageFormat method, but I can't figure out how to get the PrintRequestAttributeSet (which is not the printJob.getPrintService().getPrintAttributes()). Honestly, all I really want to know is the width and height of the page. Any ideas on how I can do that? Thanks.

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  • Catching TransactionRolledbackLocalException in Java

    - by user271858
    I receive javax.ejb.TransactionRolledbackLocalException in Websphere 7 from the container and I wonder how is it possible to catch this exception? I have a timeout set in Websphere and get this message after this time. I run session beans. I am trying to find what SQl statement was the cause of this exception. Where can i find that?

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  • What does this java output mean?!

    - by Phil
    public class Arrys { private int[] nums; //Step 3 public Arrys (int arrySize) { nums = new int[arrySize]; } public int [] getNums (){ return nums; } } Test class: public class TestArrys { public static void main(String args[]) { //Step 4 Arrys arry = new Arrys(10); System.out.println("\nStep4 "); for(int index = 0; index < arry.getNums().length; index++) { System.out.print(arry.getNums()); } } } It's incredibly simple, that is why I think I'm doing something fundamentally wrong. All I want is to display the value of the array. This is what I get back. I am totally lost, there is nothing in my book that explains this nor does googling it help. Step4 [I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440[I@1ac88440

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  • Example applications and benefits of using "C" , "C++" or "Java"

    - by Waltzy
    Ok, I'm revising for my upcoming year 2 exams on a CS course and its likely something like this will come up. my question is what is an ideal application that would especially benefit from the program features of each of the three languages? I have a vague idea but getting a second opinion could really help. JavaPortability, easy - good for GUIs. C++Fast but may requite significant changes in order to be moved from system to system, good for image processing. CI'm unsure here small embedded applications? Some clarification on this would be really appreciated, thanks again StackOverflow

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  • How to tell if there is an available thread in a thread pool in java

    - by Gormcito
    I am trying to proccess a queue of tasks from a database table as fast as possible while also limiting the number of threads to process the tasks. I am using a fixed sized thread pool with Executors.newFixedThreadPool(N); I want to know if there is a way of knowing if the thread pool is full, by that I mean are there currently 50 threads running, if so then I'll wait for a thread to be available before starting a new one instead of sleeping the main thread. Code of what I would like to do: ExecutorService executor = Executors.newFixedThreadPool(N); ResultSet results; while( true ) { results = getWaitingTasksStmt.executeQuery(); while( results.next() && executor.notFull() ) { executor.submit( new thread( new runnableInheritedClass(results) ) ); } }

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  • [java] run 2 threads simultaneously

    - by lamsaitat
    hi all, in the case of an IM client. i have made 2 separate threads to handle sending packets (by std io) and receiving packets. the question is how to make these 2 threads run simultaneously so that i can keep prompting for input while at the same time be ready to receive packets at any time? i have already tried setting a timer but the data is always lost receiving.

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  • java/swing: font size selection + rendering

    - by Jason S
    I want to create and fill/stroke a path that consists of an outer boundary which is a square of side d and an inner boundary that is the outline of any of the capital letters. How can I do this? (challenges = creating a mask from a font, and figuring out the right size/position to use)

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  • Java-Counting occurrence of word from huge textfile

    - by Naveen
    I have a text file of size 115MB. It consists of about 20 million words. I have to use the file as a word collection, and use it to search the occurrence of each user-given words from the collection. I am using this process as a small part in my project. I need a method for finding out the number of occurrence of given words in a faster and correct manner since i may use it in iterations. I am in need of suggestion about any API that i can make use or some other way that performs the task in a quicker manner. Any recommendations are appreciated.

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  • Creating Java Dialogs

    - by mike_hornbeck
    What would be the easiest way for creating a dialog: - in one window I'm giving data for envelope addressing, also set font type from list of sizes - when clicked OK, in the same window or in next window I get preview of how the envelope would look like with the given names, and used selected font size It should look similarly to this : Should I use Jdialog ? Or will JOptionPane will be enough ? The next step will be to choose color of font and background so I must keep that in mind.

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  • get attribute value from html code in java

    - by sang
    Hi All i have HTML string value and i want to get one attribute(id) value from that html String value can u help me how to do it?? String msHTMLFile = "<ABBR class='HighlightClass' id='highlight40001' style=\"BACKGROUND-COLOR: yellow\" >Fetal/Neonatal Morbidity and Mortality</ABBR>"; result should come - highlight40001;

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  • Help with enums in Java

    - by devoured elysium
    Is it possible to have an enum change its value (from inside itself)? Maybe it's easier to understand what I mean with code: enum Rate { VeryBad(1), Bad(2), Average(3), Good(4), Excellent(5); private int rate; private Rate(int rate) { this.rate = rate; } public void increateRating() { //is it possible to make the enum variable increase? //this is, if right now this enum has as value Average, after calling this //method to have it change to Good? } } This is want I wanna achieve: Rate rate = Rate.Average; System.out.println(rate); //prints Average; rate.increaseRating(); System.out.println(rate); //prints Good Thanks

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