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  • How to see "anti if" movement and its gaol?

    - by Vijay Shanker
    I have a developer for last 3 years, have been using if-else or if-else if statements a lot in my programing habit. And today, I found This link. One obvious sample i put here public void doSomthing(String target, String object){ //validate requests if(target != null && target.trim().length() < 1){ //invalid request; } //further logic } Now, I have seen this sort of check all over the places, libraries. So, I wanted to have a discussion about the worthiness of such a movement. Please let me know your views.

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  • Interview question : What is the fastest way to generate prime number recursively ?

    - by hilal
    Generation of prime number is simple but what is the fastest way to find it and generate( prime numbers) it recursively ? Here is my solution. However, it is not the best way. I think it is O(N*sqrt(N)). Please correct me, if I am wrong. public static boolean isPrime(int n) { if (n < 2) { return false; } else if (n % 2 == 0 & n != 2) { return false; } else { return isPrime(n, (int) Math.sqrt(n)); } } private static boolean isPrime(int n, int i) { if (i < 2) { return true; } else if (n % i == 0) { return false; } else { return isPrime(n, --i); } } public static void generatePrimes(int n){ if(n < 2) { return ; } else if(isPrime(n)) { System.out.println(n); } generatePrimes(--n); } public static void main(String[] args) { generatePrimes(200); }

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  • Strange performance behaviour

    - by plastilino
    I'm puzzled with this. In my machine Direct calculation: 375 ms Method calculation: 3594 ms, about TEN times SLOWER If I place the method calulation BEFORE the direct calculation, both times are SIMILAR. Woud you check it in your machine? class Test { static long COUNT = 50000 * 10000; private static long BEFORE; /*--------METHOD---------*/ public static final double hypotenuse(double a, double b) { return Math.sqrt(a * a + b * b); } /*--------TIMER---------*/ public static void getTime(String text) { if (BEFORE == 0) { BEFORE = System.currentTimeMillis(); return; } long now = System.currentTimeMillis(); long elapsed = (now - BEFORE); BEFORE = System.currentTimeMillis(); if (text.equals("")) { return; } String message = "\r\n" + text + "\r\n" + "Elapsed time: " + elapsed + " ms"; System.out.println(message); } public static void main(String[] args) { double a = 0.2223221101; double b = 122333.167; getTime(""); /*--------DIRECT CALCULATION---------*/ for (int i = 1; i < COUNT; i++) { Math.sqrt(a * a + b * b); } getTime("Direct: "); /*--------METHOD---------*/ for (int k = 1; k < COUNT; k++) { hypotenuse(a, b); } getTime("Method: "); } }

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  • Google App Engine/Simple HTML, how to write input boxes with google autocomplete

    - by Calm Storm
    I am writing a GAE application and I would like to have an input box with google auto-suggest. Specifically, when a user types "Shawshank" I would like to see google's suggestions in my drop down. Can someone tell me what are the different ways of doing this? I understand I may have to use some javascript libraries so any code samples etc will help immensely. (Pure javascript/jquery kinda solutions will be more preferable)

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  • security issue on web application using firebug

    - by Suresh S
    Guys i have developed a web application in jsp . I have many javscript validation for text validation in the jsp page.while during the testing , i enabled firebug in firefox and cleared a function that validates and submits to a servlet.The web application allows to submit garbage value of the textfiedl . how to overcome this ? any solutions?

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  • I'm confused about Polymorphism

    - by Vtanathip
    I'm know polymorphism rule that we can send it via parameter like this code interface Animal { void whoAmI(); } class A implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("A"); } } class B implements Animal{ @Override public void whoAmI() { // TODO Auto-generated method stub System.out.println("B"); } } class RuntimePolymorphismDemo { public void WhoRU(List t){ System.out.println(t.getClass()); } public static void main(String[] args) { A a = new A(); B b = new B(); RuntimePolymorphismDemo rp = new RuntimePolymorphismDemo(); rp.WhoRU(a); rp.WhoRU(b); } } but List<Example> examples = new ArrayList<Example>(); This code,I'm don't understand why we must use List. why we can't use like this? ArrayList<Example> examples = new ArrayList<Example>(); Because when we use List we can't use method that only have in ArrayList class like trimToSize() and How I know when to use or not use?

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  • Reset JPA generated value between tests

    - by Rythmic
    I'm running spring + hibernate + JUnit with springJunit4runner and transactional set to default rollback I'm using in-memory derbydb as Database. Hibernate is used as a JPA Provider and I am successfully testing CRUD kinds of stuff. However, I have a problem with JPA and the behaviour of @GeneratedValue If I run one of my tests in isolation, two entitys are persisted with id 1 and 2. If i run the whole test suite the ids are instead 6 and 7. Spring does rollbacks just fine so there are only these two entitys in the database after addition and of course zero before. But behaviour of @GeneratedValue doesn't allow me to reliable findById unless I would return the Id from the dao.add(Entity e) //method I don't feel like doing that for the sake of testing, or is it a good practise to return the entity that was persisted so I should be doing it anyway?

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  • JLabel wont change color twice

    - by Aly
    Hi, I have the following code: public class Test extends JFrame implements ActionListener{ private static final Color TRANSP_WHITE = new Color(new Float(1), new Float(1), new Float(1), new Float(0.5)); private static final Color TRANSP_RED = new Color(new Float(1), new Float(0), new Float(0), new Float(0.1)); private static final Color[] COLORS = new Color[]{ TRANSP_RED, TRANSP_WHITE}; private int index = 0; private JLabel label; private JButton button; public Test(){ super(); setLayout(new BoxLayout(getContentPane(), BoxLayout.Y_AXIS)); label = new JLabel("hello world"); label.setOpaque(true); label.setBackground(TRANSP_WHITE); getContentPane().add(label); button = new JButton("Click Me"); button.addActionListener(this); getContentPane().add(button); pack(); setVisible(true); } @Override public void actionPerformed(ActionEvent e) { if(e.getSource().equals(button)){ label.setBackground(COLORS[index % (COLORS.length - 1)]); } } public static void main(String[] args) { new Test(); } } When I run it I get the label with the TRANSP_WHITE background and then when I click the button this color changes to TRANSP_RED but when I click it again I see no change in color. Does anyone know why? Thanks

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  • Please help with my twodimensional array source code

    - by Baiba
    Here is what i have done but i have some questions: class masivins { public static void main (String args[]) { int mas[][] = {{0, 2, 7, 0, 8, 5, 3}, {0, 4, 0, 6, 0, 0, 0}, {0, 0, 0, 0, 3, 0, 0}, {7, 0, 0, 9, 1, 0, 7}, {5, 0, 4, 0, 0, 2, 0}}; int nulmas[] = new int [7]; int nul=0; for(int j=0; j<7; j++) { nul=0; for(int i=0; i<5; i++) { if(mas[i][j]==0) { nul++; } } nulmas[j]=nul; } for(int i=0; i<5; i++) { for(int j=0; j<7; j++) { System.out.println(mas[i][j]); } System.out.println(); } System.out.println(); for(int i=0; i<5; i++) { System.out.println("Zeros in each array column: " + nulmas[i]); } System.out.println(); } } so my questions are: 1) why after running project there are only 5 "Zeros in each array column....." shown? 2) what and where i need to change in this code to get out the number of column in which zeros are least?

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  • How do I reload servlet classes without restarting my web application?

    - by Ramon
    I want to reload just my web layer classes without reloading my service layer classes (which take longer to initialize and change less frequently). There are no references from my service layer into the web layer and I can create a whole new instance of the web layer without problems. I can conceive of a solution involving complicated class-loader tricks to isolate the web layer in its own class-loader and I think this is probably the only way to do this so what I'm asking is, is there a library out there which does this? I know about JavaRebel - I don't need that much power and I'm really looking for a more lightweight free solution.

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  • How to write native SQL queries in Hibernate without hardcoding table names and fields?

    - by serg555
    Sometimes you have to write some of your queries in native SQL rather than hibernate HQL. Is there a nice way to avoid hardcoding table names and fields and get this data from existing mapping? For example instead of: String sql = "select user_name from tbl_user where user_id = :id"; something like: String sql = "select " + Hibernate.getFieldName("user.name") + " from " + Hibernate.getTableName(User.class) + " where " + Hibernate.getFieldName("user.id") + " = :id";

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  • How to use ASTRewrite split one field declaration into two?

    - by user307598
    For example: private long p, q, g, h; I want to split this field declaration as: private long p; private long q, g, h; How can I use ASTRewrite to do it? I tried to use ASTNode copyFd = rewriter.createCopyTarget(fd) to copy the field declaration, modify it, then add to field declaration list, but my modification on copyFd is not seen. It's just the same to fd. Why? Anybody can help?

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  • Why does this compile?

    - by akf
    I was taken aback earlier today when debugging some code to find that something like the following does not throw a compile-time exception: public Test () { HashMap map = (HashMap) getList(); } private List getList(){ return new ArrayList(); } As you can imagine, a ClassCastException is thrown at runtime, but can someone explain why the casting of a List to a HashMap is considered legal at compile time?

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  • What's the reason behind the jumping GeneratedValue(strategy=GenerationType.TABLE) when not specifyi

    - by joeduardo
    Why do I need to add allocationSize=1 when using the @TableGenerator to ensure that the id wouldn't jump from 1, 2,... to 32,xxx, 65,xxx,... after a jvm restart? Is there a design reason for the need to specify the allocationSize? This snippet would produce the jumping ids @Id @GeneratedValue(strategy = GenerationType.TABLE) private Long id; Here's the modified snippet that produces the properly sequenced ids @Id @GeneratedValue(strategy = GenerationType.TABLE, generator = "account_generator") @TableGenerator(name = "account_generator", initialValue = 1, allocationSize = 1) private Long id;

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  • how to configure jetty 7 to use syslog or log4j

    - by egemen ozden
    I am looking for a way to direct all the jetty 7 logging to syslog. My current configuration dumps everything to JETTY_HOME/logs/.. After some initial ivestigation, it seems I should change JETTY_HOME/etc/jetty-logging.xml, but this does not look straightforward. It looks like I should create a new PrintStream implementation which sends its output to syslog and redirecting stderr and stdout to that class in jetty-logging.xml. any easier way to do that or to make jetty log directly to log4j ? Thanks

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  • How to show alert in a jsp from a servlet and then redirect to another jsp?

    - by Xaul Omar Tobar
    I tried this but does not display the message only redirects login.jsp <form method="post" action="Login_Servlet" > <input name="idUsuario" type="text"/> <input name="password" type="password" /> <button type="submit">Entrar</button> </form> Login_Servlet response.setContentType("text/html;charset=UTF-8"); PrintWriter out = response.getWriter(); String userid= request.getParameter("idUser"); String password = request.getParameter("password"); Login_Service login_Service = new Login_Service(); boolean result = login_Servicio.aut(userid, password); Usuario user = login_Servicio.getUsuariosByUsuario(userid); if(result == true){ request.getSession().setAttribute("user", user); response.sendRedirect("vistas/Inicio.jsp"); } else{ out.println("<script type=\"text/javascript\">"); out.println("alert('User or password incorrect');"); out.println("</script>"); response.sendRedirect("index.jsp"); } Is it possible to display a message like this? if so I'm doing wrong?

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  • How to get structure of a Google Protobuf message without the definition

    - by dqminh
    I have to get the message structure of a protobuf message transfered to me without the message's definition. Using UnknownFieldSet methods, I was able to get a string representation of the message as below: 1: "a" 2: { 3:"b" 4:"c" } What data structure does field 2 represent ? Using UnknownFieldSet.Field.getGroupList i was able to get the content of field 3 and 4, does that means field 2 has the "deprecated" group structure ?

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  • set arraylist element as null

    - by Jessy
    The first index is set to null (empty), but it doesn't print the right output, why? //set the first index as null and the rest as "High" String a []= {null,"High","High","High","High","High"}; //add array to arraylist ArrayList<Object> choice = new ArrayList<Object>(Arrays.asList(a)); for(int i=0; i<choice.size(); i++){ if(i==0){ if(choice.get(0).equals(null)) System.out.println("I am empty"); //it doesn't print this output } }

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  • Advice on creating simple web service

    - by London
    Hi all, I want to build simple SOAP web service. So far I've only worked with existing SOAP/Rest services. And now I'd like to create my own, simple one for starters. For example create simple hello + string web service where I provide the string in request from SOAP ui or similar tool. I have Jboss server installed already, what is the "simplest" possible way to achieve this? I realize I need interface, interfaceImpl, and a wsdl file(generated possibly). Does anyone have some useful advice for me ? thank you

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  • uploading app problem in developers site

    - by Siva K
    hi i have posted one of my app in market.android.com when i am trying to post second app it shows "You have another application on Market with the same package name. Go to that other application, and click upgrade" I dont want to upgrade it but i want my second app to be posted. When i tried to change the package name it showed lots of errors, so i decided to create the app once again in a new package and project name, it seems to be a very lengthy process.... pls help me to solve the issue bcoz i have created all my app in same package name unknowingly.......

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  • How can I split abstract testcases in JUnit?

    - by Willi Schönborn
    I have an abstract testcase "AbstractATest" for an interface "A". It has several test methods (@Test) and one abstract method: protected abstract A unit(); which provides the unit under testing. No i have multiple implementations of "A", e.g. "DefaultA", "ConcurrentA", etc. My problem: The testcase is huge (~1500 loc) and it's growing. So i wanted to split it into multiple testcases. How can organize/structure this in Junit 4 without the need to have a concrete testcase for every implementation and abstract testcase. I want e.g. "AInitializeTest", "AExectueTest" and "AStopTest". Each being abstract and containing multiple tests. But for my concrete "ConcurrentA", i only want to have one concrete testcase "ConcurrentATest". I hope my "problem" is clear. EDIT Looks like my description was not that clear. Is it possible to pass a reference to a test? I know parameterized tests, but these require static methods, which is not applicable to my setup. Subclasses of an abstract testcase decide about the parameter.

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