Char Array to String with classes

Question

I am trying to write a class that has methods according to a homework assignment. The class input is a string that is turned into an char array. I want to return the char array as a string inside the method originalChar. Here is my code:

public class Problem5 {
    public static void main(String[] args) {
        CharacterArray array1 = new CharacterArray("Cool");
        System.out.println(array1.originalChar());
    }
}

class CharacterArray {
    char[] storage;
    String formForReturn;

    CharacterArray() {
    }

    CharacterArray(String s) {
        char[] storage = new char[s.length()];
        for (int i = 0; i < s.length(); i++) {
            storage[i] = s.charAt(i);
        }
    }

    public String originalChar() {
        String formForReturn = new String(storage);
        return formForReturn;
    }
}

The error I get is NullPointerException, which to my understanding means I am trying to reference something that doesn't exist. I'm not sure how I troubleshoot this and how to resolve this problem. Some help would be much appreciated.

char[] storage is wrong. Because you create another storage which is just in that method. You should use this.storage or just remove char[] — KunLun
– KunLun, Commented Jul 5, 2020 at 20:11

Sercan · Accepted Answer · 2020-07-09 21:58:14Z

2

The way to access instance variable char[] storage; is to use this keyword which represents current object. Otherwise, with your current solution, what you return is empty which causes NullPointerException. Because you create another storage instead of using existing one in the class.

Also you can write your originalChar() method in a shorter way:

class CharacterArray {
    char[] storage;

    CharacterArray() { }

    CharacterArray(String s) {
        this.storage = new char[s.length()];
        for (int i = 0; i < s.length(); i++) {
            storage[i] = s.charAt(i);
        }
    }

    public String originalChar() {
        return new String(this.storage);
    }
}

edited Jul 9, 2020 at 21:58

answered Jul 5, 2020 at 20:15

Sercan

2,1692 gold badges14 silver badges26 bronze badges

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

1 Comment

3leggedquid Over a year ago

This worked. Thanks so much. I always get the this keyword messed up. Thanks again

Collectives™ on Stack Overflow

Char Array to String with classes

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related