JAVA EE: Java Tutorial : Java Access (Instance and Static methods)

Monday, 4 January 2016

Java Tutorial : Java Access (Instance and Static methods)

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Java Tutorial : Java Access (Instance and Static methods)

InstanceMethodTest.java

public class InstanceMethodTest
{
    int instanceVar = 10;
    static String staticVar = "Welcome";

    /*
     * Instance methods can access instance variables and instance methods
     * directly.
     * 
     * Instance methods can access class variables and class methods directly.
     */
    public void instanceMethod1()
    {
        System.out.println("instanceMethod1 is called.");
        System.out.println("instanceVar : " + instanceVar);
        instanceMethod2();
        
        System.out.println("staticVar : " + staticVar);
        staticMethod();
    }

    public void instanceMethod2()
    {
        System.out.println("instanceMethod2 is called.");
    }
    
    public static void staticMethod()
    {
        System.out.println("staticMethod is called.");
    }

}

ClassMethodTest.java

public class ClassMethodTest
{
    int instanceVar = 10;
    static String staticVar = "Welcome";

    public void instanceMethod1()
    {
        System.out.println("instanceMethod1 is called.");
    }


    /*
     * Class methods can access class variables and class methods directly.
     * 
     * Class methods cannot access instance variables or instance methods
     * directly—they must use an object reference.  Also, class methods cannot
     * use the this keyword as there is no instance for this to refer to.
     */

    public static void staticMethod()
    {
        System.out.println("staticMethod is called.");

        System.out.println("staticVar : " + staticVar);
        staticMethod();

        System.out.println("instanceVar : " + instanceVar);
        instanceMethod1();

        System.out.println(this.instanceVar);
        
        ClassMethodTest classMethodTest = new ClassMethodTest();
        
        System.out.println("instanceVar : " + classMethodTest.instanceVar);
        classMethodTest.instanceMethod1();      

    }

}