reverseString.java

public reverse(String word) {
char[] chs = word.toCharArray();
int i=0, j=chs.length-1;
while (i < j) {
 // swap chs[i] and chs[j]
  char t = chs[i];
  chs[i] = chs[j];
  chs[j] = t;
  i++; j--;
 }
}

//Another way using java utility.
import org.apache.commons.lang.StringUtils;
String reverseWords(String sentence) {
  return StringUtils.reverseDelimited(StringUtils.reverse(sentence), ' ');
}