CODEWITHSUNDEEP
java
user2782378
user2782378

Reputation:

Getting null value. Beginner

When use the interactions panel to run my code I get a null value before the result. for example when I enter: 1st word - google 2nd word - chrome

the result should be - gcohorgolme but instead it is - nullgcohorgolme

Any ideas why? Here is my code:

public class Collate{
  String result;
  String x;
  String y; 

  public String collate(String x, String y){

    for(int i = 0; i < x.length(); i++)
    {
      result += x.charAt(i);
      result += y.charAt(i);
    }
    return (result);
  }
}

Thanks a bunch!

Upvotes: 0

Views: 115

Answers (7)

SuperCamp
SuperCamp

Reputation: 36

You can always use a StringBuffer.

public static String collate(String x, String y){

    StringBuffer result = new StringBuffer();

    for(int i = 0; i < x.length(); i++)
    {
        result.append(x.charAt(i)).append(y.charAt(i));
    }

    return (result.toString());
}

Upvotes: 1

Debojit Saikia
Debojit Saikia

Reputation: 10632

4.3.1 Objects (from Java Language Specifications):

The string concatenation operator +, which, when given a String operand and a reference, will convert the reference to a String by invoking the toString method of the referenced object (using "null" if either the reference or the result of toString is a null reference), and then will produce a newly created String that is the concatenation of the two strings

And here the result String was initialized with a null reference. So to get the desired result, you need to initialize the result as:

String result="";

Upvotes: 0

David
David

Reputation: 709

You haven't initialized your result value.

Remember that you should always initialize your variables. The null happens because your result is getting initialized an then converted to a String, which is null.

Upvotes: 3

afpro
afpro

Reputation: 1103

result += x.charAt(i) is equal to result = result + x.charAt(i) but result is null at first loop.

Upvotes: 1

IHazABone
IHazABone

Reputation: 525

Initialize your result string, as String result = "";
This step should always be taken as a precaution, otherwise you may end up with a null output as you have here.

Upvotes: 2

krypton-io
krypton-io

Reputation: 713

initialize result first to empty string. 

result = "";

Upvotes: 2

Dimitar Dimitrov
Dimitar Dimitrov

Reputation: 15158

Make sure you initialize result:

  public String collate(String x, String y){
    result = ""; // <-- here

    for(int i = 0; i < x.length(); i++)
    {
      result += x.charAt(i);
      result += y.charAt(i);
    }
    return (result);
  }

Upvotes: 7

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