Nested class in for loop, will there be n instances of the class?

Question

I was wondering how a nested class works in a for loop:

• will the object of the class be destroyed after every for interation?
• will the instance of the class be destroyed automatically by "garbage"?
• once the for loop finishes will the object from the nested class persist in memory? can it be recalled from other places in the program?

This is the code:

class Outer {
  int outer_x = 100;

  void test() {
    for(int i=0; i<10; i++) {
      class Inner {
        void display() {
          System.out.println("display: outer_x = " + outer_x);
        }
      }
      Inner inner = new Inner();
      inner.display();
    }
  }
}

class InnerClassDemo {
  public static void main(String args[]) {
    Outer outer = new Outer();
    outer.test();
  }
}

Answer 1

Having a class definition inside a method is just syntax: it's still a perfectly normal class definition.

For the Inner objects (new Inner()) you create, that means:

• each object will be eligible for garbage collection just like any other object, immediately after the loop iteration
• yes, the object will eventually be garbage collected
• the object will linger until it is garbage collected, but won't be accessible from other places (since no reference to it leaked).

For the class itself, this means:

• the class will be loaded as usual (only once)
• the class will not be re-loaded on each iteration
• the class will not even be re-loaded on a second invocation of test
• the class can be GCed according to the normal rules of GCing classes (which are pretty stringent)