string reverse problem

i have written a java program开发者_开发百科 to reverse the contents of the string and display them.

here is the code..

import java.util.*;
class StringReverse
{
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
        System.out.print("Enter a string to be reversed :");
        String input = in.next();  
        char[] myArray = new char[input.length()];
        myArray = input.toCharArray();
        int frontPos=0,rearPos=(myArray.length)-1;
        char tempChar;
        while(frontPos!=rearPos)
        {
            tempChar=myArray[frontPos];
            myArray[frontPos]=myArray[rearPos];
            myArray[rearPos]=tempChar;
            frontPos++;
            rearPos--;
        }
        System.out.println();
        System.out.print("The reversed string is : ");
        for(char c : myArray)
        {
            System.out.print(c);
        }

    }
}

Now the program works fine for strings of length greater than or equal to 5. But if I give a string of length 4 as input, I get an ArrayIndexOutOfBounds Exception. What could be the problem?

The issue isn't that the input is of length 4, but that the length 4 is an even length, so your stopping condition never hits. That is, frontpos never equals rearpos for even length strings.

You should instead just make sure that frontpos is less than rearpos, changing while(frontPos!=rearPos) to while(frontPos < rearPos) should clear things up.

Would probably be easier to write with only one counter.

for(int i = 0; i < myArray.length; i++) {
  char temp = myArray[i];
  myArray[i] = myArray[myArray.length - i - 1];
  myArray[myArray.length - i - 1] = temp;
}
String reversed = new String(myArray);

Why are you making the logic so complicated. It can easily be done as:

char temp[] = new char[str.length()];
    int k = 0;

    for(int i = str.length()-1 ; i >= 0 ; i--)
    {
        temp[k] = str.charAt(i);
        k++;
    }
System.out.println(new String(temp));

public String reverse(String str)
{
    String rev = " ";
    for (int i = 0 ; i < str.length(); i++)
    {
        rev = str.charAt(i) + rev;
    }
    return rev.trim();
}

Input:

December

Output:

rebmeceD