java (day 17)practical notes

 overriding

package com.company;

class A{
    public int a;
    public int harry(){
        return 4;
    }
    public void meth2(){
        System.out.println("I am method 2 of class A");
    }
}

class B extends A{
    @Override
    public void meth2(){
        System.out.println("I am method 2 of class B");
    }
    public void meth3(){
        System.out.println("I am method 3 of class B");
    }
}



public class cwh_chapter10_method_overriding {

        public static void main(String[] args) {
            A a = new A();
            a.meth2();

            B b = new B();
            b.meth2();
        }
    }



this-super keyword
package com.company;


import javax.print.Doc;

class EkClass{
    int a;

    public int getA() {
        return a;
    }

    EkClass(int a){
        this.a = a;
    }
    public int returnone(){
        return 1;
    }
}
class DoClass extends EkClass{
    DoClass(int c){
        super(c);
        System.out.println("I am a constructor");
    }
}



public class cwh_chapter10_this_super {

        public static void main(String[] args) {
            EkClass e = new EkClass(65);
            DoClass d = new DoClass(5);
            System.out.println(e.getA());
        }
    }


constructor-inheritance
package com.company;


class Base1{
    Base1(){
        System.out.println("I am a constructor");
    }
    Base1(int x){
        System.out.println("I am an overloaded constructor with value of x as: " + x);
    }
}

class Derived1 extends Base1{
    Derived1(){
        //super(0);
        System.out.println("I am a derived class constructor");
    }
    Derived1(int x, int y){
        super(x);
        System.out.println("I am an overloaded constructor of Derived with value of y as: " + y);
    }
}

class ChildOfDerived extends  Derived1{
    ChildOfDerived(){
        System.out.println("I am a child of derived constructor");
    }
    ChildOfDerived(int x, int y, int z){
        super(x, y);
        System.out.println("I am an overloaded constructor of Derived with value of z as: " + z);
    }
}

public class cwh_chapter10_constructor_inheritance {

        public static void main(String[] args) {
            // Base1 b = new Base1();
            // Derived1 d = new Derived1();
            // Derived1 d = new Derived1(14, 9);
            // ChildOfDerived cd = new ChildOfDerived();
            ChildOfDerived cd = new ChildOfDerived(12, 13, 15);
        }
    }


inheritance

//check constructor repeat******************

//inheritance-------------child class borrowed from parent class for code reusability,for carry forwrd




package com.company;


class Base{
    public int x;

    public int getX() {//getter
        return x;
    }

    public void setX(int x) {//setter (ctrl + insert )
        System.out.println("I am in base and setting x now");
        this.x = x;
    }

    public void printMe(){
        System.out.println("I am a constructor");
    }
}

class Derived extends Base{//inheritance used extends keyword(extend class BASE) (NEW CLASS DERIVED)
    public int y;

    public int getY() {
        return y;
    }

    public void setY(int y) {
        this.y = y;
    }
}

public class cwh_chapter10_inheritance {


        public static void main(String[] args) {
            // Creating an Object of base class
            Base b = new Base();
            b.setX(4);
            System.out.println(b.getX());

            // Creating an object of derived class
            Derived d = new Derived();
            d.setY(43);
            System.out.println(d.getY());
        }
    }

constructor
package com.company;

class MyMainEmployee{
    private int id;
    private String name;

    public MyMainEmployee(){
        id = 0;
        name = "Your-Name-Here";
    }
    public MyMainEmployee(String myName, int myId){
        id = myId;
        name = myName;
    }
    public MyMainEmployee(String myName){
        id = 1;
        name = myName;
    }
    public String getName(){
        return name;
    }
    public void setName(String n){
        this.name = n;
    }
    public void setId(int i){
        this.id = i;
    }
    public int getId(){
        return id;
    }
}

public class cwh_42_constructors {
    public static void main(String[] args) {
        //MyMainEmployee harry = new MyMainEmployee("ProgrammingWithHarry", 12);
        MyMainEmployee harry = new MyMainEmployee();
        //harry.setName("CodeWithHarry");
        //harry.setId(34);
        System.out.println(harry.getId());
        System.out.println(harry.getName());
    }
}

acessmodifier-getter-setter
package com.company;

class MyEmployee{
    private int id;
    private String name;

    public String getName(){
        return name;
    }
    public void setName(String n){
        this.name = n;
    }
    public void setId(int i){
        this.id = i;
    }
    public int getId(){
        return id;
    }
}
public class cwh_40_ch9 {
    public static void main(String[] args) {
        MyEmployee harry = new MyEmployee();
        // harry.id = 45;
        // harry.name = "CodeWithHarry"; --> Throws an error due to private access modifier
        harry.setName("CodeWithHarry");
        System.out.println(harry.getName());
        harry.setId(234);
        System.out.println(harry.getId());
    }
}



oops(create own java class)

package com.company;

class Employee{
    int id;
    int salary;
    String name;
    public void printDetails(){
        System.out.println("My id is " + id);
        System.out.println("and my name is "+ name);
    }

    public int getSalary(){
        return salary;
    }
}

public class cwh_38_custom_class {
    public static void main(String[] args) {
        System.out.println("This is our custom class");
        Employee harry = new Employee(); // Instantiating a new Employee Object
        Employee john = new Employee(); // Instantiating a new Employee Object

        // Setting Attributes for Harry
        harry.id = 12;
        harry.salary = 34;
        harry.name = "CodeWithHarry";

        // Setting Attributes for John
        john.id = 17;
        john.salary = 12;
        john.name = "John Khandelwal";

        // Printing the Attributes
        harry.printDetails();
        john.printDetails();
        int salary = john.getSalary();
        System.out.println(salary);
        // System.out.println(harry.id);
        // System.out.println(harry.name);
    }
}


abstruct class
package com.company;

 abstract class Parents2{
    public  Parents2(){
        System.out.println("this is constructor");
    }
    public  void dayHello(){
        System.out.println("hello");
    }
    abstract public  void greet();
     abstract public  void greet2();
}


class Child2 extends  Parents2{
     @Override
     public void greet(){
         System.out.println("good morning");
     }@Override
    public void greet2(){
        System.out.println("good afternoon");
    }
}


abstract class Child3 extends  Parents2{
    //Class 'Child3' must either
    // be declared abstract or implement abstract method 'greet()' in 'Parents2'
     public void  th(){
         System.out.println("i am good");
     }
}

public class cwh_chapter11_abstruct_class {
    public static void main(String[] args) {
   //Parents2 p=new Parents2() {};---------------error
       //reason //Class 'Anonymous class derived from Parents2' must either be declared
       // abstract or implement abstract method 'greet()' in 'Parents2'
   Child2 c=new Child2();
   //Child3 c3 =new Child3() {---------------error
       /*
       @Overridex
       public void greet() {

       }

       @Override
       public void greet2() {

       }
   }
   */

    }
}

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