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Commit 22b6a39

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1 parent 0269e04 commit 22b6a39

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‎Constructor/Car.java‎

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package Constructor;
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class CarCreat {
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int regNum;
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private static int num=1000;
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CarCreat(){regNum=num++;}
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void cardetails(){
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System.out.println("Your car: "+regNum);
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}
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void start(){
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System.out.println("Car Starts. ");
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}
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void accelerate(){
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System.out.println("Car Accelerate. ");
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}
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void stop(){
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System.out.println("Car Stops. ");
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}
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}
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class Driver{
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String name;
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CarCreat c=new CarCreat();
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Driver(String n){
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name=n;
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}
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void driverName(){
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System.out.println(name);
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}
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}
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public class Car{
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public static void main(String... args){
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Driver dr=new Driver("xyz");
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dr.driverName();
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dr.c.cardetails();
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dr.c.start();
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Driver dr1=new Driver("abc");
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dr.driverName();
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dr1.c.cardetails();
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dr1.c.start();
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}
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}

‎Constructor/ConstEx1.java‎

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package Constructor;
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public class ConstEx1 {
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// if we won't provide any constructor compiler adds default constructor
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// int this case, ConstEx1(){} , but if we provide any other constructor
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// compiler won't add.
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int x, y;
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// no-argument constructor
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ConstEx1() {
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getX(); // we can call both static and non-static method from
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// constructor
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x = 0;
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y = 0;
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}
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// Parameterized Constructor
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ConstEx1(int l) {
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x = y = l;
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getX();
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}
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ConstEx1(int l, int m) {
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x = l;
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y = m;
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}
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static void getX() {
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System.out.println(" You're inside method getX() ");
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// return x;
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}
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public static void main(String[] args) {
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ConstEx1 c1 = new ConstEx1();
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System.out.println("[C1]X= " + c1.x + " Y= " + c1.y);
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ConstEx1 c2 = new ConstEx1(20);
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ConstEx1 c3 = new ConstEx1(12, 13);
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System.out.println("[C2]X= " + c2.x + " Y= " + c2.y);
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System.out.println("[C3]X= " + c3.x + " Y= " + c3.y);
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}
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}

‎Constructor/CopyConst.java‎

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package Constructor;
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public class CopyConst {
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double real, imaginary;
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public CopyConst(double re, double img) {
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real = re;
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imaginary = img;
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}
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// Copy Constructor
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public CopyConst(CopyConst c) {
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real = c.real;
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imaginary = c.imaginary;
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}
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@Override // toString() is the override method of Object Class
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public String toString() {
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return "(" + real + " + " + imaginary + "i)";
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}
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public static void main(String[] args) {
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CopyConst c1 = new CopyConst(10, 15);
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CopyConst c2 = new CopyConst(c1);
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CopyConst c3 = c1;
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System.out.println("[C2]" + c2); // if we directly print object Output
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// Constructor.CopyConst@6d06d69c
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System.out.println("[C3]" + c3); // on directly printing object it will
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// call toString() of Object class
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}
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}

‎Inheritance/InheritEx.java‎

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package Inheritance;
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class SuperClass {
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int i, j;
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void showij() {
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System.out.println("i and j: " + i + " " + j);
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}
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}
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class SubClass extends SuperClass {
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int k;
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void showk() {
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System.out.println("k:" + k);
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}
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void sum() {
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System.out.println(i + j + k);
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}
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}
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class InheritEx {
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public static void main(String args[]) {
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SuperClass sup = new SuperClass();
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SubClass sub = new SubClass();
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sup.i = 10;
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sup.j = 20;
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System.out.println("Contents of super class ");
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sup.showij();
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sub.i = 7;
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sub.j = 8;
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sub.k = 9;
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System.out.println("Contents of sub class");
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sub.showij();
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sub.showk();
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System.out.println("Sum of i, j and k in sub class");
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sub.sum();
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}
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}

‎Inheritance/NblockInherit.java‎

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package Inheritance;
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class Box1 {
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{
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System.out.println(1);
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}
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}
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class Box2 extends Box1 {
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{
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System.out.println(2);
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}
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}
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class Box3 extends Box2 {
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{
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System.out.println(3);
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}
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}
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public class NblockInherit {
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public static void main(String[] args) {
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Box3 c = new Box3();
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System.out.println(c);
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}
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}

‎Inheritance/SblockInherit.java‎

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package Inheritance;
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class Box11 {
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static {
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System.out.println(1);
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}
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}
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class Box12 extends Box11 {
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static {
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System.out.println(2);
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}
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}
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class Box13 extends Box12 {
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static {
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System.out.println(3);
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}
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}
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public class SblockInherit {
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public static void main(String[] args) {
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Box13 c = new Box13();
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System.out.println(c);
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}
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}

‎Inheritance/SingleLevel.java‎

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package Inheritance;
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class A {
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private int i = 12;
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protected int j = 13;
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public int k = 14;
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int m = 3;
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A() {
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System.out.println("I'm Constructor from class A.");
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}
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private void m1() {
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System.out.println("Private method of class A " + i);
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}
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protected void m2() {
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System.out.println("Protected method of class A " + j);
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m1();
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}
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public void m3() {
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System.out.println("Public method of class A " + k);
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}
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void m4() {
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System.out.println("Package method of class A" + i + " " + m);
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}
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}
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class B extends A {
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B() {
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System.out.println("I'm Constructor from class B.");
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}
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public void m5() {
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// System.out.println(i); // private variables not accessible in
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// sub-class
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System.out.println(" Method from class B. ");
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System.out.println("Protected j= " + j);
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System.out.println("public k= " + k);
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System.out.println("Package m= " + m);
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// m1(); // Private method is not accessible in sub-class
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m2();
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m3();
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m4();
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}
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}
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public class SingleLevel {
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public static void main(String[] args) {
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B b = new B();
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System.out.println("----------------------------------");
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System.out.println(" From Main method. ");
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b.m5();
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b.m4();
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System.out.println("----------------------------------");
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}
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}

‎Inheritance/TrickyEx.java‎

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package Inheritance;
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class Test {
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static int i = 56;
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static {
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i = i-- - --i;
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System.out.println("i value Static Block of Test Class: "+i);
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}
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{
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i = i++ + ++i;
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System.out.println("i value Non-Static Block of Test Class: "+i);
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}
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}
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class Test1 extends Test {
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static {
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i = --i - i--;
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System.out.println("i value Static Block of Test1 Class: "+i);
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}
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{
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i = ++i + i++;
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System.out.println("i value Non-Static Block of Test1 Class: "+i);
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}
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}
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public class TrickyEx {
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public static void main(String[] args) {
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// Test1 b = new Test1();
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// System.out.println(b.i);
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System.out.println(Test.i);
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}
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}

‎MethodOverloading/NullTest1.java‎

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package MethodOverloading;
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public class NullTest1 {
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/*
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* If more than one member method is both accessible and applicable to a method invocation,
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* it is necessary to choose one to provide the descriptor for the run-time method dispatch.
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*
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* The Java programming language uses the rule that the most specific method is chosen.
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* */
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public static void method(Object obj){
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System.out.println("method with param type - Object");
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}
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public static void method(String obj){
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System.out.println("method with param type - String");
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}
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// public static void method(StringBuffer strBuf){
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// System.out.println("method with param type - StringBuffer");
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// }
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/*
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* Why is the compiler not able to pick 'the most specific' here - because both "String" and "StringBuffer" are are sub-classes.
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of the Object class, but without being in the same inheritance hierarchy. For finding
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'the most specific' method, the compiler needs to find a method having the parameter type,
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which is a sub-class of the parameter types of all other overloaded methods.
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* */
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public static void main(String [] args){
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method(null);
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}
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}
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‎MethodOverloading/NullTest2.java‎

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package MethodOverloading;
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public class NullTest2 {
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public static void method(Object obj, Object obj1){
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System.out.println("method with param types - Object, Object");
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}
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public static void method(String str, Object obj){
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System.out.println("method with param types - String, Object");
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}
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/*
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* In this case the compiler can easily pick 'the most specific' as the method having parameter types (String, Object) as
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the other overloaded method is having its parameter types as (Object, Object) - clearly 'String' is a subclass of 'Object'
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and the other parameter is of same type, so the method with parameter types (String, Object) can be picked with ease.
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*
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* */
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public static void main(String [] args){
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method(null, null);
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}
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}

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