public void reverString(){
System.out.println("Enter value");
BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
 try{

  String str=br.readLine();
  char[] charArray=str.toCharArray();
  for(int i=charArray.length-1; i>=0; i--){
   System.out.println(charArray[i]);
  }
  }
   catch(IOException ex){
  }

public static String revString(String str){
    char[] revCharArr = str.toCharArray();
    for (int i=0; i< str.length()/2; i++){
        char f = revCharArr[i];
        char l = revCharArr[str.length()-i-1];
        revCharArr[i] = l;
        revCharArr[str.length()-i-1] = f;
    }
    String revStr = new String(revCharArr);
    return revStr;
}

看一下StringBuffer下的Java 6 API

String s = "sample";
String result = new StringBuffer(s).reverse().toString();

递归:

 public String stringReverse(String string) {
    if (string == null || string.length() == 0) {
        return string;
    }
    return stringReverse(string.substring(1)) + string.charAt(0);
 }

对于不允许StringBuilder或StringBuffer的Online Judges问题，可以使用char[]，如下所示:

public static String reverse(String input){
    char[] in = input.toCharArray();
    int begin=0;
    int end=in.length-1;
    char temp;
    while(end>begin){
        temp = in[begin];
        in[begin]=in[end];
        in[end] = temp;
        end--;
        begin++;
    }
    return new String(in);
}

1. 使用字符数组:

public String reverseString(String inputString) {
    char[] inputStringArray = inputString.toCharArray();
    String reverseString = "";
    for (int i = inputStringArray.length - 1; i >= 0; i--) {
        reverseString += inputStringArray[i];
    }
    return reverseString;
}

2. 使用StringBuilder:

public String reverseString(String inputString) {
    StringBuilder stringBuilder = new StringBuilder(inputString);
    stringBuilder = stringBuilder.reverse();
    return stringBuilder.toString();
}

OR

return new StringBuilder(inputString).reverse().toString();