Jakarta Commons Cookbook

2.9. Reversing a String

Problem

You need to reverse a string.

Solution

Use StringUtils.reverse( ). Supply a string parameter to this method, and it will return a reversed copy. The following example reverses two strings:

String original = "In time, I grew tired of his babbling nonsense.";
String reverse = StringUtils.reverse( original );
String originalGenes = "AACGTCCCTTGGTTTCCCAAAGTTTCCCTTTGAAATATATGCCCGCG";
String reverseGenes = StringUtils.reverse( originalGenes );

System.out.println( "Original: " + original );
System.out.println( "Reverse: " + reverse );
System.out.println( "\n\nOriginal: " + originalGenes );
System.out.println( "Reverse: " + reverseGenes );

The output contains a reversed string along with an original string:

Original: In time, I grew tired of his babbling nonsense.
Reverse: .esnesnon gnilbbab sih fo derit werg I ,emit nI

Original: AACGTCCCTTGGTTTCCCAAAGTTTCCCTTTGAAATATATGCCCGCG
Reverse: GCGCCCGTATATAAAGTTTCCCTTTGAAACCCTTTGGTTCCCTGCAA

Discussion

Reversing a String is easy, but how would you rearrange the words in a sentence? StringUtils.reverseDelimited( ) can reverse a string of tokens delimited by a character, and a sentence is nothing more than a series of tokens separated by whitespace and punctuation. To reverse a simple sentence, chop off the final punctuation mark, and then reverse the order of words delimited by spaces. The following example reverses an unrealistically simple English sentence:

public Sentence reverseSentence(String sentence) { String reversed ...