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are wrapper classes intialized to zero?  RSS feed

 
Ranch Hand
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if we declare Integer i;

does i get intialized to zero???
 
Bartender
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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.
 
Sheriff
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Hmmm... If only there were some way to test this.
 
Ranch Hand
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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.

 
Java Cowboy
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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.
 
Ranch Hand
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Why classes like "Integer" called wrapper?What is the reason?
 
Bartender
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Because they wrap around a primitive. That way you can store primitives in a Collection.
 
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