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are wrapper classes intialized to zero?

archu sweet
Ranch Hand

Joined: Mar 07, 2011
Posts: 66

if we declare Integer i;

does i get intialized to zero???
Matthew Brown
Bartender

Joined: Apr 06, 2010
Posts: 4344
    
    8

No. Because it's a reference type, it gets initialised to null. Assuming you're talking about a member variable, that is - variables declared in methods aren't initialised to anything.
marc weber
Sheriff

Joined: Aug 31, 2004
Posts: 11343

Hmmm... If only there were some way to test this.


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kumarjit banerjee
Ranch Hand

Joined: Mar 27, 2011
Posts: 32

archu sweet wrote:if we declare Integer i;

does i get intialized to zero???



Consider the following example

The output of the program is null. The reason is that when Integer i; is declared the reference variable i is initialized to null since it is an instance variable. Now the obvious question is that the program should throw a NullPointerException but this not the case.
System.out.println(i); invokes the below overloaded version of println of the class java.io.PrintStream.



Now consider the below method of java.lang.String

This provides the solution to the query.

Jesper de Jong
Java Cowboy
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Joined: Aug 16, 2005
Posts: 14074
    
  16

Kumarjit: Thanks for your answer. Please UseCodeTags when you post source code - as you can see, the code will be formatted in a much more readable way when you use them.

Anchu: As you can see, you could have checked this out yourself by writing a small program. Try writing lots of little programs to test out features of Java - trying things out yourself is one of the best ways to learn.


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abalfazl hossein
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Joined: Sep 06, 2007
Posts: 635
Why classes like "Integer" called wrapper?What is the reason?
Wouter Oet
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Joined: Oct 25, 2008
Posts: 2700

Because they wrap around a primitive. That way you can store primitives in a Collection.


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