Reverse a string in Java

Question

I have "Hello World" kept in a String variable named hi.

I need to print it, but reversed.

How can I do this? I understand there is some kind of a function already built-in into Java that does that.

Related: Reverse each individual word of “Hello World” string with Java

Answer 1

You can use this:

new StringBuilder(hi).reverse().toString() 

StringBuilder was added in Java 5. For versions prior to Java 5, the StringBuffer class can be used instead — it has the same API.

Answer 2

For Online Judges problems that does not allow StringBuilder or StringBuffer, you can do it in place using char[] as following:

public static String reverse(String input){     char[] in = input.toCharArray();     int begin=0;     int end=in.length-1;     char temp;     while(end>begin){         temp = in[begin];         in[begin]=in[end];         in[end] = temp;         end--;         begin++;     }     return new String(in); }