0

How to reverse a string in java programming language? without use of any built in function.

Siddharth Maratha
  • 1
  • 1
  • 1
    Copy the string into a character array, reverse that, make a new String out of it. – Thilo Mar 20 '21 at 07:10
  • 1
    Iterate over the string in the reverse order, read the characters and append them to a new, initially empty string. – Alex Sveshnikov Mar 20 '21 at 07:10
  • 3
    The problem is ill-defined. You **have** to call some built-in functions (methods, actually) to even get to the content of a `String` (for example `toCharArray`). – Joachim Sauer Mar 20 '21 at 07:20
  • This question is meaningful and may be resolved _without_ built-in functions only in languages like good old `C` where a String is a synonym of char array `char[]` or a sequence of char ending with `\0` (ASCIIZ strings) referred by `char*` pointer. – Nowhere Man Mar 20 '21 at 08:30

1 Answers1

0

Here is one way you can do it by converting it into a char array and prepending each element of the array onto an empty string:

public class ReverseString{
    public static void main(String[] args){
        String str = "abcde";
        //make char array
        char[] array = new char[str.length()]; 
        for (int i = 0; i < str.length(); i++) { 
            array[i] = str.charAt(i); 
        } 

        //reverse by prepending to a string
        String newString = "";
        for (char character : array){
            newString = character + newString;
        }
        
        System.out.println(newString);
    }
}
Jamin
  • 1,362
  • 8
  • 22
  • Two _built-in functions_ `length()` and `charAt()` are used here :) And use of intermediate `array` along with the additional loop seems to be redundant. – Nowhere Man Mar 20 '21 at 07:31
  • Could be wrong, but I think the OP may have meant to say only using built in functions. The code is redundant, but I wanted to go with what some other comments were saying about iterating to explain the idea. – Jamin Mar 20 '21 at 07:34