Printing reverse of any String without using any predefined function?

Question

How to print the reverse of the String java is object orientated language without using any predefined function like reverse()?

Answer 1

import java.util.Scanner;
public class StringReverse {
    public static void main(String[] args) {
        //Read user Data From Console
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter Your String:");
        //Take an String so that it can Store the string data 
        String s1 = sc.nextLine();
        //split the string and keep in an array
        String[] s2 = s1.split(" ");
        String s3 = " ";
        //reverse  the string and placed in an String s3
        for (int i = 0; i < s2.length; i++) {
            for (int j= s2[i].length()-1;j>=0;j--) {
                s3 += s2[i].charAt(j);
            }//for
            s3 += " ";
        }//for

        System.out.println("After Reverse: "+s3);

    }//main
}//StringReverse

Answer 2

Here's a recursive solution that just prints the string in reverse order. It should be educational if you're trying to learn recursion. I've also made it "wrong" by actually having 2 print statements; one of them should be commented out. Try to figure out which mentally, or just run experiments. Either way, learn from it.

static void printReverse(String s) {
    if (!s.isEmpty()) {
        System.out.print(s.substring(0, 1));
        printReverse(s.substring(1));
        System.out.print(s.substring(0, 1));
    }
}

Bonus points if you answer these questions:

• What is its stack requirement? Is it prone to stack overflow?
• Is it a tail recursion?

Answer 3

String x = "stack overflow";
String reversed = "";
for(int i = x.length()-1 ; i>=0; i--){
    reversed = reversed+ x.charAt(i);
}
System.out.println("reversed string is : "+ reversed);

Answer 4

Well, printing itself would suggest a predefined function...

Presumably, though, you could obtain the characters and concatenate them manually in reverse (i.e. loop over it backwards). Of course, you could say concatenation is a predefined function... so maybe the char array itself. But again... why?

Is the source allowed to contain "egaugnal detatneiro tcejbo si avaj" ;-p

Also - note that string reversal is actually pretty complex if you consider unicode combining characters, surrogate pairs, etc. You should note the caveat that most string reversal mechanisms will only deal with the more common cases, but may struggle with i18n.

Answer 5

public class ReverseString {

public static void main(String[] args) {

    reverseString("HELLO");
}

public static String reverseString(String s){
    char []arr=s.toCharArray();
    for(int i= (arr.length)-1;i>=0;i--){
        System.out.print(arr[i]);
    }
    String str=String.copyValueOf(arr);
    return str;
}

Answer 6

Try this:

public  class Test {

    public static void main(String[] args) {
        String s = "welcome";   
    for( int i=0, j = (s.length())-1; i <= j; j-- ) {   
      char c=s.charAt(j);
      System.out.print(c);
    }
    }
}