Easy way to reverse String

Question

Without going through the char sequence is there any way to reverse String in Java

Answer 1

Here I have a sample of the same using substring method and o(n) without using any nethods from string . I am aware that using substring will hold complete string memory.

for(int i = 0; i < s.length(); i++)    {
    s = s.substring(1, s.length() - i) + s.charAt(0) + s.substring(s.length() - i);
    System.out.println(s);
}

This might help you!!

Answer 2

I have not seen any easy way. Here is the suitable way to do:

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Using the loop:

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    String d = "abcdefghij";
    char b[] = new char[d.length()];// new array;
    int j=0; // for the array indexing
    for(int i=d.length()-1;i>=0;i--){
        b[j] = d.charAt(i); // input the last value of d in first of b i.e. b[0] = d[n-1]
        j++;
    }
    System.out.println("The reverse string is: "+String.valueOf(b));

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Output is The reverse string is: jihgfedcba

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The simple logic is:

array[i] = array[n-i]; where i is the Iteration and n is the total length of array

Answer 3

This is a way to do so using recursion -

public static String reverse(String s1){
        int l = s1.length();
        if (l>1)
                return(s1.substring(l-1) + reverse(s1.substring(0,l-1)));
        else
                return(s1.substring(0));
}

Answer 4

Use StringBuilder's or StringBuffer's method... reverse()

 public class StringReverse
{
  public static void main(String[] args)
  {
  String string=args[0];
  String reverse = new StringBuffer(string).reverse().toString();
  System.out.println("\nString before reverse: "+string);
  System.out.println("String after reverse: "+reverse);
  } 
} 

StringBuffer is thread-safe, where as StringBuilder is Not thread safe..... StringBuilder was introduced from Java 1.5, as to do those operations faster which doesn't have any Concurrency to worry about....

Answer 5

You may use StringBuilder..

String word = "Hello World!";
StringBuilder sb = new StringBuilder(word);

System.out.print(sb.reverse());

Answer 6

You can use String buffer to reverse a string.

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

one more interesting way to do this is recursion.

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