Question

Discuss the difference between an "instance member variable" and a "static member variable" Give an example to support your answer.

Answer 1

Instance Variables hold values that must be referenced essential parts of an object's state. Instance Variables are created for every object of class.
It is not shared by all the objects of class.
Instance Variables are accessed by objects of class.

Static Variable would only be one copy of each class variable per class, regardless of how many objects are created from it
It is shared by all the objects of class.
To access Static Variable we do not need any object. We just use class name to access it.

Example:

//TestCode.java
public  class TestCode {
    public int instanceVariable;
    public static int staticVariable = 0;

    public TestCode(int instanceVariable) {
        this.instanceVariable = instanceVariable;
        staticVariable += 1;
    }

    public static void main(String[] args) {
        TestCode t1 = new TestCode(5);
        System.out.println("t1.instanceVariable = "+t1.instanceVariable);
        System.out.println("TestCode.staticVariable = "+TestCode.staticVariable);

        TestCode t2 = new TestCode(10);
        System.out.println("t2.instanceVariable = "+t2.instanceVariable);
        System.out.println("TestCode.staticVariable = "+TestCode.staticVariable);
    }
}