command line arguments - ArrayIndexOutOfBoundsException when launching a java program

Question

I am currently working on an assignment but there seems to be a problem when running my code.

public class caesar {
    public static void main(String args[]) {
        String inputString = args[0];
        char inputArray[] = inputString.toCharArray();
        int shiftLength = Integer.parseInt(args[1]);
        System.out.println("Input: " + inputString);
        String outputString = "";

This is the error I am receiving:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at caesar.main(caesar.java:3)

Answer 1

You are not passing command line arguments to your program and don't check whether they are passed. To pass arguments launch your program like

java caesar arg0 arg1

For example:

java caesar somestring 10

To do this in NetBeans 8.0.2 IDE, open Project Properties, select the Run item, then specify the arguments there:

You may probably also want to check the number of passed arguments in advance to output the friendly error message. For example:

public static void main(String args[]) {
    if(args.length != 2) {
        System.err.println("Usage: java caesar <inputString> <shift>");
        return;
    }
    ... // the rest of your code
}