reverse a string in java

1// reverse a string using reverse() method of StringBuilder class
2class ReverseUsingReverseMethod
3{
4   public static void main(String[] args)
5   {
6      String str = "Hello world Java";
7      StringBuilder sb = new StringBuilder();
8      // append string to StringBuilder
9      sb.append(str);
10      sb = sb.reverse();
11      // printing reversed String
12      System.out.println(sb);
13   }
14}

1// reverse a string using character array
2class ReverseUsingCharacterArray
3{
4   public static void main(String[] args)
5   {
6      String str = "HelloWorldJava";
7      char[] ch = str.toCharArray();
8      for(int a = ch.length - 1; a >= 0; a--)
9         System.out.print(ch[a]);
10   }
11}

1Solution 1 
2
3public static String StrReverse(String str) {
4
5String reverse="";
6
7for(int i=str.length()-1; i >= 0; i--)
8
9reverse += str.toCharArray()[i];
10
11 
12
13return  reverse;
14
15}
16
17 
18
19Solution 2 (using string buffer)
20
21public  static String  Reverse(String str) {
22
23return new StringBuffer(str).reverse().toString());
24
25}

1public class StringReverseExample{
2   public static void main(String[] args) {
3      String string = "abcdef";
4      String reverse = new StringBuffer(string).reverse().toString();
5      System.out.println("\nString before reverse: "+string);
6      System.out.println("String after reverse: "+reverse);
7   }
8}

1// reverse a string using toCharArray() method
2class ReverseUsingToCharArrayMethod
3{
4   public static void main(String[] args)
5   {
6      String str = "Hello World Java";
7      char[] chTemp = str.toCharArray();
8      int left, right = 0;
9      right = chTemp.length - 1;
10      for(left = 0; left < right ; left++, right--)
11      {
12         // swap values
13         char temp = chTemp[left];
14         chTemp[left] = chTemp[right];
15         chTemp[right]=temp;
16      }
17      for(char c : chTemp)
18         System.out.print(c);
19      System.out.println();
20   }
21}

1// reverse a string using ByteArray
2class ReverseStringByteArray
3{
4   public static void main(String[] args)
5   {
6      String input = "HelloWorld";
7      // getBytes() method to convert string into bytes[].
8      byte[] strByteArray = input.getBytes();
9      byte[] output = new byte[strByteArray.length];
10      // store output in reverse order
11      for(int a = 0; a < strByteArray.length; a++)
12         output[a] = strByteArray[strByteArray.length - a - 1];
13      System.out.println(new String(output));
14   }
15}

1// Not the best way i know but i wanted to challenge myself to do it this way so :)
2public static String reverse(String str) {
3  char[] oldCharArray = str.toCharArray();
4  char[] newCharArray= new char[oldCharArray.length];
5  int currentChar = oldCharArray.length-1;
6  for (char c : oldCharArray) {
7    newCharArray[currentChar] = c;
8    currentChar--;
9  }
10  return new String(newCharArray);
11}

1public class Main {
2
3    public static void main(String[] args) {
4	// Write a Java program to reverse a string.
5        Scanner input = new Scanner(System.in);
6        System.out.println("Enter the String:");
7        char[] letters = input.nextLine().toCharArray();
8        System.out.println(" Reverse String");
9        for(int i = letters.length -1; i >= 0; i--){
10            System.out.print(letters[i]);
11        }
12    }
13}
14

1As we know that String is immutable. String class do not have reverse() method.