Where to construct an object

Question

Possible Duplicate:
Instance variable initialization in java

Hello, can someone tell me what the difference / pros or cons of creating an object with the declaration of the class instance vars ie..

public class ClassName{
    Object o = new Object();
}

to in the contructor

public class ClassName{ 
    Object o;
    public ClassName(){
        o = new Object();
    }
}

thank you!

possible duplicate:http://stackoverflow.com/questions/3918578/should-i-initialize-variable-within-constructor-or-outside-constructor — Emil, Oct 25 '10 at 11:37

score 1 · Answer 1 · answered Oct 25 '10 at 11:39

1

Well in the upper case there's always an object made if the class is loaded, inthe lower case you're only create the object if the class is instantiated.

I guess the second way is always the way to go if you don't make the field o static.

answered Oct 25 '10 at 11:39

Akku

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score 0 · Answer 2 · answered Oct 25 '10 at 11:38

0

In your case it is effectively the same.

The difference would be if

there were other fields that depend on field "o" or
there were other Constructors

answered Oct 25 '10 at 11:38

Peter Knego

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score 0 · Answer 3 · answered Oct 25 '10 at 12:08

I usually construct it at the declaration if it's a "trivial" default-constructor thing. I put it in the constructor if

I need different initializations for different constructors (obviously)
The initialization depends on some argument of the constructor (obviously)
The initialization of the field requires any work, such as getting the value from some where else.

As always when there is no semantical difference, rule of thumb is: Go for the alternative that you find most readable.

Where to construct an object

3 Answers3