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Rocky Bhai
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Uploaded on 1st-Feb - 2nd commit.
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‎javabasic/sample/AnonymousClass.java‎

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package sample;
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// This example is to test the anonymous classes
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class Books {
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public void name() {
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System.out.println("Printing book name.");
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}
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public void author() {
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System.out.println("Calling author inside Book class.");
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}
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}
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interface Paper {
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public void pages();
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public void thick();
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}
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public class AnonymousClass {
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public static void main(String[] args) {
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Books b1 = new Books() {
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// Creating an override method while creating an object
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@Override
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public void name() {
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System.out.println("Printing book name inside main.");
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}
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public void author() {
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System.out.println("Book has been written by a famous author.");
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}
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public void pages() {
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System.out.println("Printing the number of pages inside main.");
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}
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};
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b1.name();
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b1.author();
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// The following will produce an error as the pages
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// method is not existing inside Books class.
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// b1.pages();
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Paper p1 = new Paper() {
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@Override
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public void pages() {
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System.out.println("Page size is A4");
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}
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public void thick() {
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System.out.println("Page is thick");
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}
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};
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p1.pages();
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p1.thick();
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}
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}

‎javabasic/sample/GenericsWildcard.java‎

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Original file line numberDiff line numberDiff line change
@@ -9,24 +9,84 @@ class Machine1 {
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public String toString() {
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return "This is a Machine.";
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}
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public void start() {
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System.out.println("Machine starting...");
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}
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public void stop() {
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System.out.println("Machine stopping...");
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}
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}
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class Camera extends Machine1 {
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@Override
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public String toString() {
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return "This is a Camera.";
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}
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// Overrides the start method in Machine1 class
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public void start() {
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System.out.println("Camera starting...");
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}
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public void snap() {
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System.out.println("Photo snapped..");
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}
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}
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class Car extends Machine1 {
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@Override
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public String toString() {
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return "This is a Car.";
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}
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public void stall() {
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System.out.println("Car has stalled...");
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}
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public void sleep() {
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System.out.println("Car is sleeping...");
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}
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}
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class Bus extends Machine1 {
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@Override
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public String toString() {
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return "This is a Bus.";
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}
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// Overrides the start method in Machine1 class
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public void start() {
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System.out.println("Bus has started...");
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}
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// Overrides the stop method in Machine1 class
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public void stop() {
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System.out.println("Bus has stopped...");
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}
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}
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public class GenericsWildcard {
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// Used wildcard "?" as to pass object of any class
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public static void showList(ArrayList<?> list) {
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// Using Object as it is the super class
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for (Object value : list) {
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System.out.println(value);
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}
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}
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public static void showListExtends(ArrayList<? extends Machine1> list) {
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// Changing to Machine1 from Object as this method
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// is extended to Machine1.
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for (Machine1 value : list) {
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System.out.println(value);
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value.start();
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value.stop();
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// Cannot use the snap method from the Camera class
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// as it is not available in Machine1 class.
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// The following will throw an error.
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// value.snap();
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}
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}
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public static void main(String[] args) {
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ArrayList<Machine1> list1 = new ArrayList<Machine1>();
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@@ -37,9 +97,56 @@ public static void main(String[] args) {
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list2.add(new Camera());
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list2.add(new Camera());
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ArrayList<Car> list3 = new ArrayList<Car>();
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list3.add(new Car());
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list3.add(new Car());
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ArrayList<String> list4 = new ArrayList<String>();
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list4.add("Dog");
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list4.add("Cat");
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list4.add("Horse");
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ArrayList<Bus> list5 = new ArrayList<Bus>();
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list5.add(new Bus());
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list5.add(new Bus());
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showList(list1);
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showList(list2);
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}
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showList(list3);
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showList(list4);
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}
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System.out.println("*************************");
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showListExtends(list1);
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System.out.println();
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// Camera does not have stop method and hence
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// it reaches out to the stop method in the
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// parent class - Machine1
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showListExtends(list2);
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System.out.println();
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// Since car class does not have start / stop
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// method, it will use the start /stop method of
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// the parent class i.e. Machine1
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showListExtends(list3);
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System.out.println();
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// Cannot use object list4 as with showListExtends method as
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// it extends to Machine1 class. It will throw an error
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// if you try to use it:
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// showListExtends(list4);
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// Since Bus class has stop / start method, it will
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// use it's own methods and will override the methods
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// provided by the parent class - Machine1
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showListExtends(list5);
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System.out.println("*************************");
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}
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}

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