String Reverser

With paper and pencil, reversing a string is easy. Copy characters from the original string right to left to the new string left to right.

The reverse() method in the following program follows that idea. The variable j indexes characters in the original string starting at the rightmost character, data.length()-1, and moves left until it reaches the first character. Each character is appended on the right of a new String.

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 )
  {
    System.out.println( reverse( "Hello" ) );
  }
}

The body of the for loop executes once per character.