CODEWITHSUNDEEP
javamemory-leaksstaticclass-variables
Mac
Mac

Reputation: 1495

Defining a static List could lead to memory leakage?

If I define a static variable in my class as follows:

class MyClass
{
  private static List<String> list = new ArrayList<String>();
}

Can list cause memory leakage? If yes, then how?

Upvotes: 2

Views: 2119

Answers (4)

Sotirios Delimanolis
Sotirios Delimanolis

Reputation: 279890

The snippet of code you posted is a memory leak in the sense that if you never clear elements from that list or set it to null, it will keep growing and not get garbage collected.

With non-static lists (instance or local scoped lists), this would happen much less often. With non-static variables, once the instance goes out of scope, so does the variable (and possibly the object), so it can get garbage collected. With static variable, they can never go out of scope (unless you set the reference to null , which you can't do on final) since they're linked to the class.

Upvotes: 2

Evgeniy Dorofeev
Evgeniy Dorofeev

Reputation: 135992

It's not necessarily static Lists (Collection) that may cause a memory leak. If we have a long-living Collection (eg cache) we should limit its size somehow, eg by removing old object form it.

Upvotes: 1

rocketboy
rocketboy

Reputation: 9741

Technically it is a memory leak only if it is out of garbage collector's reach. On the other hand, if it is in memory for extended periods even when you don't have a use for it, well that's a logical flaw and it will keep the related objects from getting gc'ed too. The memory will be reclaimed only when the class is unloaded.

Upvotes: 1

Bogdan M.
Bogdan M.

Reputation: 2181

Static variables are in classes alloaced in a special memory place meaning, in your app exsists only 1 array Myclass.list, and the thing is they are not dynamic. So your list has to have a fixed size.

public final  static String[] list=new String[]
    {"str1", //0
    "str2", //1
    "str3", //2
    "str4", //3
    };

You can't modify those values, by result i doubt it will cause leaks.

Upvotes: -1

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