C:\>java myProgram "Input String"

String Reverser

This program reverses the characters of its argument. It does this by copying characters one at a time from right to left from the input string to the end of a reversed string. The method data.charAt(j) returns the character at position j in the string data.

public class ReverseTester
{

  public static String reverse( String data )
  {
    String rev = new String();

    for ( int j=data.length()-1; j >= 0; j-- )
      rev += data.charAt(j);

    return rev;
  }

  public static void main ( String[] args )
  {
    if ( args.length > 0 )
      System.out.println( reverse( args[0] ) );
  }
}

Here is a sample run of this program:

C:\cs151\Notes/chap49D>java  ReverseTester "This is argument 0"
0 tnemugra si sihT

The string that follows the program name on the command line is available to the program in slot zero of the array of arguments, args. The main() method calls the reverse() method with that string and gets back a reversed string.