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Loading, Linking And Initialization

By Value or By Reference

  • Primitive variables are passed by value in a method and their values don’t change in calling method.
  • Changes in the reference variables which are done in the called method, are also seen by the calling method.

Loading, Linking and Initialization

  • Loading
    • Loads the binary representation of class.
  • Linking
    • Verification
    • Preparation
    • Resolution
  • Initialization
    • Defaulting of member variables.
    • Difference between object initialization and static initialization.
					public class MyClass {
    static {
        ("Static initialization block");

    public static int myField = 42;

    public static void main(String[] args) {
        System.out.println("Main method");


In this example:

  • Class loading occurs when the program is run.
    Linking includes
  • verification, preparation (allocating memory for myField), and resolution.
  • Initialization includes executing the static
    initialization block and initializing myField.

    When you run the program, you’ll see the following output:
					Static initialization block
Main method

Comparing Objects

  • Compares the reference pointed by two objects is same or not.
  • Not very meaningful, until you implement equals() and hashCode() methods of Object class.

The Garbage Collector

  • JVM runs the garbage collector program to free the unused memory.
  • So unlike C++, in java you don’t have to explicitly free memory references.