Paul's Advice to Newbies, #1

Question

It's easy to run a quick test using a short class file and a main() method, like this:
public class test {
  public static void main(String[] argv) {
    // put your test code in this method
    System.out.println("get output like this");
    // get arguments like this:
    if (argv.length > 0) {
      String firstArgument = argv[0];
      System.out.println("the first argument was: " + firstArgument);
}And compile and run it from the command line.
You can figure out some of your questions about java almost immediately with simple tests like this. For example:
public class test {
  public static void main(String[] argv) {
    // can I compare two instances of Double, initialized with the same
    // double primitive value, with "=="?
    Double double1 = new Double(5.62);
    Double double2 = new Double(5.62);
    if (double1 == double2)
      System.out.println("Two Double instances can be compared meaningfully with ==");
    else
      System.out.println("Two Double instances can NOT be compared meaningfully with ==");
}Compile and run:
javac test.java
java testand you'll see how == works with Double objects (it doesn't check for mathematical equivalency).

Answer 1

I tried your example but I get NoClassDefFoundError and also my computers beeping at me in a funny way. Heeellllpppp mmmeeeeee!!!!
:)