Inheritance

 

Cedvelde gorduyumuz kimi varis klas ferqli paketlerin icinden yalniz public ve protected fieldleri gore biler. Eyni paketdedilerse o zaman default (package private) olanlarida gore biler. 

package main.example3;

public class Parent {

    public static int a = 1;
    public int b = 2;
    protected int c = 3;
    private int d = 4;
    int e = 5;

    public static void method1() {
        System.out.println("static method1 in Parent");
    }

    public void method2() {
        System.out.println("public method2 in Parent");
    }

    protected void method3() {
        System.out.println("protected method3 in Parent");
    }

    void method4() {
        System.out.println("default method4 in Parent");
    }
}

package main.example3;

public class Child extends Parent {

    public static int a = 11;
    public int b = 22;
    protected int c = 33;
    private int d = 44;
    int e = 55;

    public static void method1() {
        System.out.println("static method1 in Child");
    }

    public void method2() {
        System.out.println("public method2 in Child");
    }

    protected void method3() {
        System.out.println("protected method3 in Child");
    }

    void method4() {
        System.out.println("default method4 in Child");
    }
}
package main.example3;

public class Main {
    public static void main(String[] args) {
        Child child = new Child();
        System.out.println(child.a);
        System.out.println(child.b);
        System.out.println(child.c);
        System.out.println(child.e);
        child.method1();
        child.method2();
        child.method3();
        child.method4();

        System.out.println("-------------------------------------");

        Parent child1 = new Child();
        System.out.println(child1.a); // variable hidden
        System.out.println(child1.b); // variable hidden
        System.out.println(child1.c); // variable hidden
        System.out.println(child1.e); // variable hidden
        child1.method1();
        child1.method2();
        child1.method3();
        child1.method4();
    }
}
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*** Interesting cases ***
package main.example4;

public class Parent {
    protected int i = 3;
    protected boolean b = false;
    protected static String s = "Parent";

    public static void f() {
        System.out.println("f() in Parent");
    }

    public void g() {
        System.out.println("g() in Parent");
    }
}
package main.example4;

public class Child extends Parent {
    private int i = 5;
    private boolean b = true;
    private static String s = "Child";

    private static void f() {
        System.out.println("f() in Child");
    }

    private void g() {
        System.out.println("g() in Child");
    }
}
Niye Child klasda f() ve g() metodlarini private ede bilmirik? Eslinda cavab cox sadedir:
polimorfizme esasen biz : Parent parent = new Child(); yaza bilerik, bu zaman biz: parent.f()
dedikde ne baw verecek? Beli duzdur sistem cawacaq. Bu da sade cavab.
Bes yaxwi bu zaman bawqa sual ortaya cixir: f() metodunun access modifier-ini niye deyiwe 
bilmirik, biz axu onsuzda parent.g() dedikde zaten bu Parentin icindeki metodu cagirir yeni 
bu istisna hali idi axi? 
Bu da cox sadedir: private etsek bu zaman bu metodu gore bilmeyeceyik, lakin bu ixtiyar niye 
elimizden alinsinki duzdur? Menasiz seslenir. default etsek yeni package-private o zaman 
problem aradan qalxmalidir duzdu? Cavab: bele bu polimorfizmi proqramci bawqa package-de 
iwledecek. Yene menasiz seslenir. protected etsek yene eyni bawqa package anlayiwi ile qarwila
wiriq.

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*** Java-da static, private, final olan metodlar static olaraq baglanirlar.