How to print (but not return) a String recursively using Java?

Question

I hate to abuse SO for homework but I'm in a pickle. Basically, my instructor wants me to do this:

Write a recursive method to print a String backwards.

The method header is: public void printBackwards1(String s)
The print statement must be before the recursive call.
The method should not alter or reverse the String, only print it backwards.

After that, they want me to do the same thing but have the print statement after the call.

I'm stumped. I already whipped up a normal-person recursive method:

public static String reverseString(String input) {
        if(input.equals("")) {
            return input;
        }
        else {
            return(reverseString(input.substring(1)) + input.substring(0, 1));
        }
}

But the print stuff has me scratching my head. Thanks in advance!

use System.out.println("your text"+var);

amkz
– amkz

2016-03-01 07:28:33 +00:00
Commented Mar 1, 2016 at 7:28 — amkz
– amkz, Commented Mar 1, 2016 at 7:28

Eran · Accepted Answer · 2016-03-01 07:28:08Z

7

Just print whatever you are currently concatenating to the String :

public static void reverseString(String input) {
    if(input.equals("")) {
        return;
    }
    else {
        reverseString(input.substring(1));
        System.out.print(input.charAt(0));
    }
}

or shorter :

public static void reverseString(String input) {
    if(input.length() > 0) {
        reverseString(input.substring(1));
        System.out.print(input.charAt(0));
    }
}

answered Mar 1, 2016 at 7:28

Eran

395k57 gold badges726 silver badges793 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

SomeJavaGuy · Accepted Answer · 2016-03-01 07:32:38Z

0

To answer the other alternative. You have to do the same basicly, despite that you need to keep in mind that you do print before doing the recursive call. Due to this you have to print the last letter before doing the recursive call, compared to the other solution from @Eran, where you print the first one.

private static void printBackwards2(String input) {
    if (input.equals("")) {
        return;
    } else {
        // Print the last char
        System.out.print(input.substring(input.length()-1, input.length()));
        // Recursive call without the last char by using substring
        printBackwards2(input.substring(0,input.length()-1));
    }
}

answered Mar 1, 2016 at 7:32

SomeJavaGuy

7,3872 gold badges24 silver badges33 bronze badges

Comments

Billydan · Accepted Answer · 2016-03-01 07:55:33Z

if I understand well you should print a "reverse" string using recursive call, if so, use for the first question:

public static void reverseString ( String input ) {
    if ( input != null ) {
        if ( input.length () <= 1 ) {
            System.out.print ( input );
        }else{
           System.out.print ( input.charAt ( input.length ()-1 ));
           reverseString ( input.substring ( 0, input.length ()-1) );
        }
    }
}

and for the second question

 public static void reverseString ( String input ) {
    if ( input != null ) {
        if ( input.length () <= 1 ) {
            System.out.print ( input );
        }else{
           reverseString ( input.substring ( 1, input.length ()) );
           System.out.print ( input.charAt ( 0 ));
        }
    }
}

Collectives™ on Stack Overflow

How to print (but not return) a String recursively using Java?

3 Answers 3

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related