This is a scjp mock exam question. Suppose I have the following two files: package pkg; public class Kit { public String glueIt (String a, String b) {return a+b;} } import pkg.*; class UseKit { public static void main(String[]args) { String s = new Kit().glueIt(args[1],args[2]); System.out.println(s); } }...
Hello, I've just created a project on Eclipse and imported some source files (existing project). But I can't compile it ! Ok, the project has got several source files, so I wanted to compile only the Main.java file (with eclipse not in the command line, in the command line it worked!) but all what I get is this error : http://www.scre...
Given the default classpath: /foo And this directory structure: foo | test | xcom |--A.class |--B.java And these two files: package xcom; public class A { } package xcom; public class B extends A { } Which allows B.java to compile? (Choose all that apply.) A. Set the current directory to xcom then invoke jav...
we have a list of domain objects needing to be edited on an html page. For example, the command & domain objects: class MyCommand { List<Person> persons; } class Person { String fname; String lname; } Then, the HTML I expect to have the Spring MVC tag libraries generate is like this: <form> <input name="persons[0].fn...
If I have a volatile boolean (let's call it valid), is the following piece of code thread-safe in Java? if (valid) return; valid = true; Or, do I need to synchronize since valid is set to true only if it's false (hence set of valid depends on its current value)? ...
I installed eclipse on a new unubtu install, via the package manager. I have Galileo. I copied my home directory from an older machine, and tried to open that workspace. Now I dont see any java perspective. (Possibly, all the info above is not relevant, but I just wanted to add any possible info, as this a clean install of Eclipse via p...
Hi, at the moment I have this: import java.util.*; import java.io.*; import java.io.BufferedReader; import java.io.FileReader; public class StudentID { public static void main(String[] args)throws Exception{ System.out.println ("Please enter StudentID: "); BufferedReader reader = new BufferedReader (new FileReader("CW2_data.c...
I'm writing an eclipse plugin, and I'm layering some simple figures (i.e. view elements) together to create diagrams. A simple component looks like this The drum icon on the right is part of a tiny widget drawer. And the incomplete line underneath it is trying to represent multiplicity, but it's being blocked by the widget drawer. ...
Given this code: public class Messager implements Runnable { public static void main(String[] args) { new Thread(new Messager("Wallace")).start(); new Thread(new Messager("Gromit")).start(); } private String name; public Messager(String name) { this.name...
I have a loop that spawns a lot of threads. These threads contains, among other things, 2 (massive) StringBuilder objects. These threads then run and do their thing. However, I noticed that after a certain amount of threads, I get strange crashes. I know this is because of these StringBuilder, because when I reduce their initial capacit...
I have three packages in NetBeans 6.7 that i want to generate a UML Class diagram automatically for. I have created the new Model by reverse engineering my project, but when i highlight all three packages under the 'Model' heading and select 'Create diagram from selected elements' i just end up with 3 green boxes. I can create separate d...
Suppose a thread A is running. I have another thread, B, who's not. B has been started, is on runnable state. What happens if I call: B.join()? Will it suspend the execution of A or will it wait for A's run() method to complete? ...
So, my problem is the following: I have a mail client that I wrote in Java and I cannot send mails through SMTP after I check my mails with POP3. The exception I caught says that the transport protocol = null. The code is working fine, because I have no issue before POP3 connection. I am sure I close that connection and they are all pr...
I'm creating subprocesses in this way: String command = new String("some_program"); Process p = Runtime.getRuntime().exec(command); How I can get that subprocess id? P.S. I'm working on Linux. ...
I'm using JNA to call Carbon APIs. The particular API call that I want to call takes a CFBooleanRef as a parameter. The values, kCFBooleanTrue and kCFBooleanFalse, are declared as direct extern references in the header files. How can I get references to those two values on the Java side, so that I can pass the values to the API call ? ...
Hi, I have an RMI client/server set-up on two machines that works fine in a simple situation when the server doesn't require a client-side defned class. However, when I need to use a class defined on the client side I am unable to have the server unmarshall those classes. I suspect this is an issue with my java.rmi.server.codebase prop...
I need to use custom filters, so I need to convert some long log4j.properties files to log4j.xml. Is anyone aware of a tool to do this, or willing to contribute one they have used? Searching has thus far turned up no such tool. ...
I created this silly program to play with wait() public class WaitTest { public static void main(String [] args) { System.out.print("1 "); synchronized(args){ System.out.print("2 "); try { args.wait(); args.notifyAll(); } catch(InterruptedException e){ System.out.pri...
Given the code: class Car{ Engine engine; } class SportCar extends Car{ SportChair chair; } Is it valid to say that 'SportCar "has-a" Engine and a SportChair'? Or the only valid affirmations are: 'SportCar "has-a" SportChair' and 'Car "has-a" Engine' ? ...
Hi, I wonder if it's a big error (in small one class Java program) when I define variable in a class level rather that using the constructor? Can we do that? The method body will be the same in both cases. Many thanks! eg. public class test{ static int column1 = 0; static int column2 = 1; public static void main(S...