recursive string reversal- reverse string

msi_333 · **Posted:** Tue Dec 02, 2008 1:30 pm

If you want to to reverse a string . I will show you two ways the first one is using the reverse method in jdk ,it is powerful function and easy .

Code:

public class MyClass {
       public String reverse(String newstring) {
            if ((null == newstring) || (newstring.length() <= 1)) {
                return newstring;
            }
            return new StringBuffer(newstring).reverse().toString();
        }
}

Notice that is no need to reverse a string with length =1 .

another solution is using recursion ,yes recursion , the idea is basic ,i know many programmers don't like recursion , but it is easy if you just think in it for a minute . ,take a look to code .

Code:

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

other solutions you may need it or think about ,

1- Do a swap in StringBuffer

Code:

  public String reverseusingswap(String newstring) {
            if ((null == newstring) || (newstring.length()  <= 1 )) {
                return newstring;
            }
            StringBuffer stringresult = new StringBuffer(newstring);
            for (int i = 0; i < (newstring.length() / 2); i++) {
                int swapIndex = newstring.length() - 1 - i;
                char swap =  stringresultcharAt(swapIndex);
                stringresult.setCharAt(swapIndex,  stringresult.charAt(i));
                 stringresult.setCharAt(i, swap);
            }
            return  stringresult.toString();
        }

2. Swap an array

Code:

public String reverse(String newstring) {
            if ((null == newstring) || (newstring.length() <= 1)) {
                return newstring;
            }
            char[] chars = newstring.toCharArray();
            int right = chars.length - 1;
            for (int left = 0; left < right; left++) {
                char swap = chars[left];
                chars[left] = chars[right];
                chars[right--] = swap;
            }
            return new String(chars);
        }

I hope it is useful for you

recursive string reversal- reverse string

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