Java's null value is added to the String

Question

Yesterday I was working on an android project & found that null value too is concatenated to a String also it effects the String length , while empty string doesn't have any effect. Why is it so ?

UPDATED QUESTION : Why is it so ? null is supposed to hold nothing !

import java.util.*;
import java.lang.*;
import java.io.*;


class Sample
{
    public static void main (String[] args) 
    {
    String nullVar  = null;
    String emptyVar = "";


    String newNullVar = nullVar + "Some,String";
    String newEmptyVar = emptyVar + "Some,String";



    System.out.println(newNullVar + " & length is " +newNullVar.length());
    System.out.println(newEmptyVar +  " & length is " +newEmptyVar.length());


    }
}

OUTPUT :

nullSome,String & length is 15
Some,String & length is 11

Output Online

What do you mean *"Why"* ? Do you want to know why Java (most languages in fact) is designed like this ? — Denys Séguret, Apr 15 '14 at 12:50
possible duplicate of [Java Strings subtle differences](http://stackoverflow.com/questions/22969348/java-strings-subtle-differences) — Not a bug, Apr 15 '14 at 12:51
Having `""` and `null` behave the same would *not* be useful. — Denys Séguret, Apr 15 '14 at 12:51
It is so strange , possible duplicate got 20 upvotes and mine question is getting down votes . — Sachin Gadagi, Apr 15 '14 at 12:54
@SachinGadagi It is not a duplicate at all! Your question is like: "why if i try to multiply two double and then to assign the result to an int the code is not compiled?" Or "why when i get the length of a String i use length() and for an array I use length?". These are very basic questions, it seems that you don't have the basis for programming in Java. — mat_boy, Apr 15 '14 at 12:57

NPE · Accepted Answer · 2014-04-15T13:06:22.520

5

The null reference is rendered as "null" because the JLS says so:

If the reference is null, it is converted to the string "null" (four ASCII characters n, u, l, l).

On the other hand, the empty string is a sequence consisting of zero characters, and this is how it is rendered.

edited Apr 15 '14 at 13:06

answered Apr 15 '14 at 12:53

NPE

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`because the JLS says so` is the right answer. +1 – njzk2 Apr 15 '14 at 13:03
1

Perfect username for an answer ;) – Rogue Apr 15 '14 at 13:10
@Rogue Can you explain please :) ? – mat_boy Apr 15 '14 at 13:13

score 0 · Answer 2 · edited Apr 15 '14 at 13:02

0

because that way if you try to print a null abject, you will get a "null" that is a little more helpfull than a void. for example

Integer i;
try{
    i = Integer.parseInt(str);
}catch(NumberFormatException e){
    //we don't care
}
System.out.println(i);

edited Apr 15 '14 at 13:02

njzk2

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answered Apr 15 '14 at 12:52

Lesto

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Java's null value is added to the String

2 Answers2