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public String reverse(String str){
	char[] array = str.toCharArray();
	int len = array.length -1;
	int mid = len/2;
 	for(int i = 0; i<=mid; i++)[
	  char temp = array[i];
  	  array [i] = array [len - i];
	   array [len -i] = temp;

return new String[array];
}

Here is an in-place solution:

public class ReverseString {

	public static String reverseMyString(String inputString)
	{
		if(inputString==null)
			return inputString;
		char[] inputArray=inputString.toCharArray();
		int start=0;
		int end=inputArray.length-1;
		while(start<end)
		{
			inputArray[start]=(char) (inputArray[start]^inputArray[end]);
			inputArray[end]=(char) (inputArray[start]^inputArray[end]);
			inputArray[start]=(char) (inputArray[start]^inputArray[end]);
			start++;
			end--;
		}
		return new String(inputArray);
	}
	
	public static void main(String[] args)
	{
		System.out.println(reverseMyString("vaibhav"));
	}
}

Efficiency suggestions are invited. :)

public String reverse(String s)
{
if (s.length() <= 1 || null==s)
{
return s;
}
return reverse(s.substring(1, s.length())) + s.charAt(0);
}

public String reverse( String s )
{
    return ( new StringBuffer( s ) ).reverse().toString();
}

public class reverseStr {


public static void main(String[] args) {
String str="lalabc";
String rev=new StringBuffer(str).reverse().toString();
System.out.println("reverse string is this "+rev);
}

}

public class Reverse {

	public static void main(String args[]) throws IOException {
		String chr;
		InputStreamReader r = new InputStreamReader(System.in);
		BufferedReader br = new BufferedReader(r);
		System.out.println("Enter your String: ");
		chr = br.readLine();
		String reverse = "";
		int len = chr.length();

		for (int i = len - 1; i > -1; i--) {
			reverse = reverse + chr.charAt(i);

		}
		System.out.println("Reversed String is:\t" + reverse);
	}}

import java.text.ParseException;
import java.util.Scanner;

public class ReverseString {
    public static void main(String[] args) throws ParseException {
        Scanner input = new Scanner(System.in);
        String string = input.nextLine();
        ReverseString ob = new ReverseString();
        System.out.println("The reverse of " + string + " is :" + ob.reverseString(string));
    }

    public String reverseString(String str) {

        char[] ch = str.toCharArray();
        StringBuilder s = new StringBuilder();
        for (int i = ch.length - 1; i >= 0; i--) {
            s.append(ch[i]);
        }
        return s.toString();
    }

}

import java.text.ParseException;
import java.util.Scanner;

public class ReverseString {
    public static void main(String[] args) throws ParseException {
        Scanner input = new Scanner(System.in);
        String string = input.nextLine();
        ReverseString ob = new ReverseString();
        System.out.println("The reverse of " + string + " is :" + ob.reverseString(string));
    }

    public String reverseString(String str) {

        char[] ch = str.toCharArray();
        StringBuilder s = new StringBuilder();
        for (int i = ch.length - 1; i >= 0; i--) {
            s.append(ch[i]);
        }
        return s.toString();
    }
}