Swap Numbers, Help!

Question

I'm new to Java and I'm wondering why this code won't work.
And if you can write this program where it'll just swap two numbers from a user input, how would write it. Help would be greatly appreciated.
class SwapNumbers {
     String[] collectNums;
     public static void main (String arguments[]) {
          SwapNumbers sn = new SwapNumbers();
          for (int i = 0; i < arguments.length; i++) {
               sn.collectNums[i] = arguments;
          String ghostNum;
          sn.ghostNum = sn.collectNum[1];
          sn.collectNums[1] = sn.collectNums[0];
          sn.collectNums[0] = sn.ghostNum;
          System.out.println(sn.collectNums[0], sn.collectNums[1]);

Answer 1

Use methods to do the work, that way you can extend the functionality in the future to handle more than 2 values, for example.
package com.stuff.jdc;
public class SwapValues {
     private String[] values;
     public static void main(String[] args) {
          SwapValues sn = new SwapValues(args);
          System.out.print("Values as entered: ");
          sn.displayNumbers();
          sn.swapValues();
          System.out.print("Values after swapping: ");
          sn.displayNumbers();
      * Constructor.
      * @param args
      * The array of command line arguments
     public SwapValues(String[] args) {
          if (args.length < 2 || args.length > 2) {
               throw new IllegalArgumentException("Must specify exactly 2 arguments");
          values = args;
     public void swapValues() {
          String temp = values[1];
          values[1] = values[0];
          values[0] = temp;
     public void displayNumbers() {
          System.out.println("[" + values[0] + "," + values[1] + "]");
}