Question

Anyone could explain what happens memory wise (Stack & Heap) in this example? If I understand it correctly, java stores objects on the heap, so i1 will be on the heap… same with string? But what about i2, considering it is a class field declaration.

public ExampleClass {
   Integer i1=new Integer(1);
   int i2 = 2;
   String str = "abc";
}

Answer 1

Nothing happens until you have some code like new ExampleClass(). Once you do that, a new object is allocated on the heap. Included in that will be references to i1, i2, and str. I’m guessing that since you’re not in a method, that i2 will be automatically converted behind the scenes to the equivalent of Integer i2 = new Integer(0). All 3 of these references will be pointing to objects also allocated on the heap. Note that strings are immutable so if there is already a String with the value "abc", then the reference may point to that.