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  • Java Clock Assignment

    - by Mike S
    For my assignment we are suppose to make a clock. We need variables of hours, minutes, and seconds and methods like setHours/getHours, setMinutes/getMinutes, setSeconds/getSeconds. Now the parts of the assignment that I am having trouble on is that we need a addClock() method to make the sum of two clock objects and a tickDown() method which decrements the clock object and a tick() method that increments a Clock object by one second. Lastly, the part where I am really confused on is, I need to write a main() method in the Clock class to test the functionality of your objects with a separate Tester class with a main() method. Here is what I have so far... public class Clock { private int hr; //store hours private int min; //store minutes private int sec; //store seconds //Default constructor public Clock () { setClock (0, 0, 0); } public Clock (int hours, int minutes, int seconds) { setTimes (hours, minute, seconds); } public void setClock (int hours, int minutes, int seconds) { if(0 <= hours && hours < 24) { hr = hours; } else { hr = 0; } if(0 <= minutes && minutes < 60) { min = minutes; } else { min = 0; } if(0 <= seconds && seconds < 60) { sec = seconds; } else { sec = 0; } } public int getHours ( ) { return hr; } public int getMinutes ( ) { return min; } public int getSeconds ( ) { return sec; } //Method to increment the time by one second //Postcondition: The time is incremented by one second //If the before-increment time is 23:59:59, the time //is reset to 00:00:00 public void tickSeconds ( ) { sec++; if(sec > 59) { sec = 0; tickMinutes ( ); //increment minutes } } public void tickMinutes() { min++; If (min > 59) { min = 0; tickHours(); //increment hours } } public void tickHours() { hr++; If (hr > 23) hr = 0; } }

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  • DWR and other possible tools for build java application level Ajax framework

    - by Fazal
    I would assume that this question would have been asked in different ways already, but I could not find one so posting it. Sorry if its a repetition The basic idea which I am trying to explore is to design a common Ajax framework/API for our application. The main requirement is to have a common framework in the product which every module in the application can call whenever it needs to provide Ajax behavior. We basically have a page based application and not everything would be Ajax for sure. Mostly it will be smaller pieces of work which Ajax will handle. We have used GWT and it works great. But we have some constraints because of which certain areas in the application need to build standard jsp and html pages only I know little bit about dwr and it looks very promising (as even answered by some people). I wanted to know what are the other possible frameworks like dwr which I can evaluate too, before making the decision

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  • "Dynamic" java validation framework?

    - by pihentagy
    AFAIK JSR-303 is the standard bean validation system. I don't know whether it could do validations like this (I guess no): if an object has a deleted flag set, you cannot modify the object you cannot change the start date property, after the date is passed you cannot decrease some integer properties in the bean So how can I handle validations, which depend on the previous state of an object? I would like to solve problems like that in hibernate3.5 - spring3 - JPA2 environment. Thanks My solution was to mess with hibernate, reload the object to see the old state (after evicting the new object). This time I need some smarter solution...

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  • Using mail servers in java

    - by sword101
    greeting all i want to use a mail server where the users send emails to it and then i parse this emails then do some action please suggest me what mail server to be used and where to start some links,tutorials,guide is very appreciated .

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  • Java ternary operator and boxing Integer/int?

    - by Markus
    I tripped across a really strange NullPointerException the other day caused by an unexpected type-cast in the ternary operator. Given this (useless exemplary) function: Integer getNumber() { return null; } I was expecting the following two code segments to be exactly identical after compilation: Integer number; if (condition) { number = getNumber(); } else { number = 0; } vs. Integer number = (condition) ? getNumber() : 0; . Turns out, if condition is true, the if-statement works fine, while the ternary opration in the second code segment throws a NullPointerException. It seems as though the ternary operation has decided to type-cast both choices to int before auto-boxing the result back into an Integer!?! In fact, if I explicitly cast the 0 to Integer, the exception goes away. In other words: Integer number = (condition) ? getNumber() : 0; is not the same as: Integer number = (condition) ? getNumber() : (Integer) 0; . So, it seems that there is a byte-code difference between the ternary operator and an equivalent if-else-statement (something I didn't expect). Which raises three questions: Why is there a difference? Is this a bug in the ternary implementation or is there a reason for the type cast? Given there is a difference, is the ternary operation more or less performant than an equivalent if-statement (I know, the difference can't be huge, but still)?

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  • Java - SwingWorker - problem in done() method

    - by Yatendra Goel
    I am using javax.swing.SwingWorker for the first time. I want to update a JLabel from the interim result published by the swing worker as follows: publish("Published String"); Now to update the JLabel, I have coded the following: process(List<String> chunks) { if (chunks.size() > 0) { String text = chunks.get(chunks.size() - 1); label.setText(text); } } The above code works but my problem(or to be more specific, my doubt) is as follows: The above swing worker task is an annonymous inner class so it can access label field. But what if I want to make the swing worker class a non-inner class. Should I need to pass label as an argument to the constructor of swing worker class so that the process() method can access. Or Is there any other way? What approach does other developer follow to update UI components from the swing worker class' result when the swing worker class is not an inner class?

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  • Java: Set<E> collection, where items are identified by its class

    - by mschayna
    I need Set collection, where its items will be identified by items class. Something like ReferenceIdentityMap from Appache Collections, but on class scope i.e. two different instances of same class must be identified as same in this collection. You know, it is a violation of equals()/hashCode() identity principle but in occasional use it makes sense. I have done this in simple class backing with Map<Class<? extends E>, E>, but due to simplicity it doesn't implement Set<E>. There may be a more elegant solution, decorator of any Set<E> would be great. Is there any implementation of such collection there (Apache/Google/something/... Collections)?

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  • Question about layout in java.

    - by extro
    I have two panels main_panel and child_panel. I have set layout for main_panel by using "main_panel.setLayout(flowlayout)" and added child_panel in main_panel by using "main_panel.add(child_panel)". This child_panel gets added to main_panel but its position is at the cross-section of horizontal midpoint and top vertical section of screen. But I want child_panel to be at the top left corner, something I could have done by using "child_panel.setlocation(a,b)" method, if I have set the Layout of main_panel as NULL. I have used flowlayout here because I want components in the JPanel to keep adjusting with the size of JFrame. So question is, can I add child_panel to main_panel at the exact location I want, even if I set the Layout of main_panel as not NULL.

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  • Java JEditorPane

    - by ikurtz
    ChatGUI im using 2 JEditorPane to transfer text from one to another. once i have transfered the data i do the following: JEditorPane.setText(null); JEditorPane.setCaretPosition(0); but as you can see from the attached image the return action makes the prompt appear a row down. how can i fix this?

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  • Java - If statement with String comparison fails

    - by Andrea
    I really don't know why the if statement below is not executing: if (s == "/quit") { System.out.println("quitted"); } Below is the whole class. It is probably a really stupid logic problem but I have been pulling my hair out over here not being able to figure this out. Thanks for looking :) class TextParser extends Thread { public void run() { while (true) { for(int i = 0; i < connectionList.size(); i++) { try { System.out.println("reading " + i); Connection c = connectionList.elementAt(i); Thread.sleep(200); System.out.println("reading " + i); String s = ""; if (c.in.ready() == true) { s = c.in.readLine(); //System.out.println(i + "> "+ s); if (s == "/quit") { System.out.println("quitted"); } if(! s.equals("")) { for(int j = 0; j < connectionList.size(); j++) { Connection c2 = connectionList.elementAt(j); c2.out.println(s); } } } } catch(Exception e){ System.out.println("reading error"); } } } } }

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  • Strange/simple batch question regarding Java/Ant

    - by Monster
    For my company, I'm making a batch script to go through and compile the latest revisions of code for our current project. I'm using Ant to build the class files, but encountered a strange error. One of the source files imports .* from a directory, where there are no files (only folders), and in fact, the folders needed are imported right after. It compiles perfectly fine in Eclipse, but I'm using an Ant script to automate it outside of the IDE, and Javac throws an error when it encounters this line. Is there any automated procedure I can use to ignore/suppress this error with javac in Ant? I'd even go so far as to create a dummy file in the importing directory, but all of that in contained in a Jar file I don't wish to have to decompress and then recompress with the dummy file. Thanks!

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  • Java HashSet using a specified method

    - by threenplusone
    I have a basic class 'HistoryItem' like so: public class HistoryItem private Date startDate; private Date endDate; private Info info; private String details; @Override public int hashCode() { int hash = (startDate == null ? 0 : startDate.hashCode()); hash = hash * 31 + (endDate == null ? 0 : endDate.hashCode()); return hash; } } I am currently using a HashSet to remove duplicates from an ArrayList on the startDate & endDate fields, which is working correctly. However I also need to remove duplicates on different fields (info & details). My question is this. Is there a way to specify a different method which HashSet will use in place of hashCode()? Something like this: public int hashCode_2() { int hash = (info == null ? 0 : info.hashCode()); hash = hash * 31 + (details == null ? 0 : details.hashCode()); return hash; } Set<HistoryItem> removeDups = new HashSet<HistoryItem>(); removeDups.setHashMethod(hashCode_2); Or is there another way that I should be doing this?

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  • JTable horizontal scrollbar in Java

    - by Mr CooL
    Is there any way to enable horizontal scrollbar whenever necessary?? The situation was as such: I've a JTable on Netbeans, one of the cells, stored a long length of data. Hence, I need to have horizontal scrollbar. Anyone has idea on this? THanks in advance for any helps..

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  • how to generate a random String? in java

    - by chandra wibowo
    hi everyone, i have an object called Student, and it has studentName, studentId, studentAddress, etc. for the studentId, i have to generate random string consist of seven numeric charaters, eg. studentId = getRandomId(); studentId = "1234567" <-- from the random generator. and i have to make sure that there is no duplicate id. thanks in advance

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  • Java/swing: console component?

    - by Jason S
    I am looking for a component I can use in Swing that acts as a GUI console which has a text area with scrollbars that can be set to a particular font has an InputStream and an OutputStream that a host application can obtain accepts keyboard input, prints it onto the end of the console text, and sends that input to the InputStream prints the OutputStream text to the end of the console has some kind of FIFO-ish property whereby the amount of text displayed in the console can be limited by automatically discarding the oldest text, when appropriate allows copy (but not cut or paste or any other editing) of the console text to the system clipboard This is kind of like the Console tab in Eclipse. Are there any good libraries that provide this?

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  • Java Conversion of byte[] into a srting and then back to a byte[]

    - by Sid
    I am working on a proxy server. I am getting data in byte[] which i convert into a string to perform certain operations. Now when i convert this new string back into a byte [] it causes unkonw problems. So mainly its like i need to know how to correctly convert a byte[] into a string and then back into a byte[] again. I tried to just convert the byte[] to string and then back to byte[] again (to make sure thats its not my operations that are causing problems). So its like: // where reply is a byte[] String str= new String(reply,0, bytesRead); streamToClient.write(str.getBytes(), 0, bytesRead); is not equivalent to streamToClient.write(reply, 0, bytesRead); my proxy works fine when i just send the byte[] without any conversion but when i convert it from byte[] to a string and then back to a byte[] its causes problems. can some one please help? =]

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  • How is Java Process.getOutputStream() Implemented?

    - by Amit Kumar
    I know the answer depends on the particular JVM, but I would like to understand how it is usually implemented? Is it in terms of popen (posix)? In terms of efficiency do I need to keep something in mind (other than using a Buffered stream as suggested by the javadoc). I would be interested to know if there is a general reference about implementations of JVMs which answers such questions.

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  • Java threadpool functionality

    - by cpf
    Hi stackoverflow, I need to make a program with a limited amount of threads (currently using newFixedThreadPool) but I have the problem that all threads get created from start, filling up memory at alarming rate. I wish to prevent this. Threads should only be created shortly before they are executed. e.g.: I call the program and instruct it to use 2 threads in the pool. The program should create & launch the first 2 Threads immediately (obviously), create the next 2 to wait for the previous 2, and at that point wait until one or both of the first 2 ended executing. I thought about extending executor or FixedThreadPool or such. However I have no clue on how to start there and doubt it is the best solution. Easiest would have my main Thread sleeping on intervals, which is not really good either... Thanks in advance!

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  • Java - Is Set.contains() broken on OpenJDK 6?

    - by Peter
    Hey, I've come across a really strange problem. I have written a simple Deck class which represents a standard 52 card deck of playing cards. The class has a method missingCards() which returns the set of all cards which have been drawn from the deck. If I try and compare two identical sets of missing cards using .equals() I'm told they are different, and if I check to see if a set contains an element that I know is there using .contains() I am returned false. Here is my test code: public void testMissingCards() { Deck deck = new Deck(true); Set<Card> drawnCards = new HashSet<Card>(); drawnCards.add(deck.draw()); drawnCards.add(deck.draw()); drawnCards.add(deck.draw()); Set<Card> missingCards = deck.missingCards(); System.out.println(drawnCards); System.out.println(missingCards); Card c1 = null; for (Card c : drawnCards){ c1 = c; } System.out.println("C1 is "+c1); for (Card c : missingCards){ System.out.println("C is "+c); System.out.println("Does c1.equal(c) "+c1.equals(c)); System.out.println("Does c.equal(c1) "+c.equals(c1)); } System.out.println("Is c1 in missingCards "+missingCards.contains(c1)); assertEquals("Deck confirm missing cards",drawnCards,missingCards); } (Edit: Just for clarity I added the two loops after I noticed the test failing. The first loop pulls out a card from drawnCards and then this card is checked against every card in missingCards - it always matches one, so that card must be contained in missingCards. However, missingCards.contains() fails) And here is an example of it's output: [5C, 2C, 2H] [2C, 5C, 2H] C1 is 2H C is 2C Does c1.equal(c) false Does c.equal(c1) false C is 5C Does c1.equal(c) false Does c.equal(c1) false C is 2H Does c1.equal(c) true Does c.equal(c1) true Is c1 in missingCards false I am completely sure that the implementation of .equals on my card class is correct and, as you can see from the output it does work! What is going on here? Cheers, Pete

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  • String replaceAll method (Java)

    - by Mr CooL
    I have following problem, Code: String a="Yeahh, I have no a idea what's happening now!"; System.out.println(a); a=a.replaceAll("a", ""); System.out.println(a); Before removing 'a', result: Yeahh, I have no a idea what's happening now! Actual Result: After removing 'a', result: Yehh, I hve no ide wht's hppening now! Desired Result: Yeahh, I have no idea what's happening now! Anyone can gimme some advices to achieve my desired result?

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  • java: how to convert a file to utf8

    - by Enrique San Martín
    Hi, i have a file that have some non-utf8 caracters (like "ISO-8859-1"), and so i want to convert that file (or read) to UTF8 encoding, how i can do it? The code it's like this: File file = new File("some_file_with_non_utf8_characters.txt"); /* some code to convert the file to an utf8 file */ ... edit: Put an encoding example

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  • Java downcasting dilemma

    - by Shades88
    please have a look at this code here. class Vehicle { public void printSound() { System.out.print("vehicle"); } } class Car extends Vehicle { public void printSound() { System.out.print("car"); } } class Bike extends Vehicle{ public void printSound() { System.out.print("bike"); } } public class Test { public static void main(String[] args) { Vehicle v = new Car(); Bike b = (Bike)v; v.printSound(); b.printSound(); Object myObj = new String[]{"one", "two", "three"}; for (String s : (String[])myObj) System.out.print(s + "."); } } Executing this code will give ClassCastException saying inheritance.Car cannot be cast to inheritance.Bike. Now look at the line Object myObj = new String[]{"one", "two", "three"};. This line is same as Vehicle v = new Car(); right? In both lines we are assigning sub class object to super class reference variable. But downcasting String[]myObj is allowed but (Bike)v is not. Please help me understand what is going on around here.

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  • Java style FOR loop in a clojure interpeter ?

    - by Kevin
    I have a basic interpreter in clojure. Now i need to implement for (initialisation; finish-test; loop-update) { statements } inside my interpreter. I will attach my interpreter code I got so far. Any help is appreciated. Interpreter (declare interpret make-env) ;; (def do-trace false) ;; ;; simple utilities (def third ; return third item in a list (fn [a-list] (second (rest a-list)))) (def fourth ; return fourth item in a list (fn [a-list] (third (rest a-list)))) (def run ; make it easy to test the interpreter (fn [e] (println "Processing: " e) (println "=> " (interpret e (make-env))))) ;; for the environment (def make-env (fn [] '())) (def add-var (fn [env var val] (cons (list var val) env))) (def lookup-var (fn [env var] (cond (empty? env) 'error (= (first (first env)) var) (second (first env)) :else (lookup-var (rest env) var)))) ;; -- define numbers (def is-number? (fn [expn] (number? expn))) (def interpret-number (fn [expn env] expn)) ;; -- define symbols (def is-symbol? (fn [expn] (symbol? expn))) (def interpret-symbol (fn [expn env] (lookup-var env expn))) ;; -- define boolean (def is-boolean? (fn [expn] (or (= expn 'true) (= expn 'false)))) (def interpret-boolean (fn [expn env] expn)) ;; -- define functions (def is-function? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'lambda (first expn))))) (def interpret-function (fn [expn env] expn)) ;; -- define addition (def is-plus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '+ (first expn))))) (def interpret-plus (fn [expn env] (+ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define subtraction (def is-minus? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '- (first expn))))) (def interpret-minus (fn [expn env] (- (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define multiplication (def is-times? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '* (first expn))))) (def interpret-times (fn [expn env] (* (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define division (def is-divides? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '/ (first expn))))) (def interpret-divides (fn [expn env] (/ (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define equals test (def is-equals? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '= (first expn))))) (def interpret-equals (fn [expn env] (= (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define greater-than test (def is-greater-than? (fn [expn] (and (list? expn) (= 3 (count expn)) (= '> (first expn))))) (def interpret-greater-than (fn [expn env] (> (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define not (def is-not? (fn [expn] (and (list? expn) (= 2 (count expn)) (= 'not (first expn))))) (def interpret-not (fn [expn env] (not (interpret (second expn) env)))) ;; -- define or (def is-or? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'or (first expn))))) (def interpret-or (fn [expn env] (or (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define and (def is-and? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'and (first expn))))) (def interpret-and (fn [expn env] (and (interpret (second expn) env) (interpret (third expn) env)))) ;; -- define with (def is-with? (fn [expn] (and (list? expn) (= 3 (count expn)) (= 'with (first expn))))) (def interpret-with (fn [expn env] (interpret (third expn) (add-var env (first (second expn)) (interpret (second (second expn)) env))))) ;; -- define if (def is-if? (fn [expn] (and (list? expn) (= 4 (count expn)) (= 'if (first expn))))) (def interpret-if (fn [expn env] (cond (interpret (second expn) env) (interpret (third expn) env) :else (interpret (fourth expn) env)))) ;; -- define function-application (def is-function-application? (fn [expn env] (and (list? expn) (= 2 (count expn)) (is-function? (interpret (first expn) env))))) (def interpret-function-application (fn [expn env] (let [function (interpret (first expn) env)] (interpret (third function) (add-var env (first (second function)) (interpret (second expn) env)))))) ;; the interpreter itself (def interpret (fn [expn env] (cond do-trace (println "Interpret is processing: " expn)) (cond ; basic values (is-number? expn) (interpret-number expn env) (is-symbol? expn) (interpret-symbol expn env) (is-boolean? expn) (interpret-boolean expn env) (is-function? expn) (interpret-function expn env) ; built-in functions (is-plus? expn) (interpret-plus expn env) (is-minus? expn) (interpret-minus expn env) (is-times? expn) (interpret-times expn env) (is-divides? expn) (interpret-divides expn env) (is-equals? expn) (interpret-equals expn env) (is-greater-than? expn) (interpret-greater-than expn env) (is-not? expn) (interpret-not expn env) (is-or? expn) (interpret-or expn env) (is-and? expn) (interpret-and expn env) ; special syntax (is-with? expn) (interpret-with expn env) (is-if? expn) (interpret-if expn env) ; functions (is-function-application? expn env) (interpret-function-application expn env) :else 'error)))

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