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‎java-interview-questions/core-java/methods/DeepCopy.java‎

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package methods;
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/**
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* In the deep copy, we create a clone which is independent of original object and making changes in the cloned object should not affect original object.
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* So for deep copy we need to ensure all the member class also implement the Cloneable interface and override the clone() method of the object class.
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*/
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import java.util.ArrayList;
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class DeepCopy1 {
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int x, y;
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}
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class DeepCopy2 implements Cloneable {
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int a, b;
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DeepCopy1 c = new DeepCopy1();
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public Object clone() throws CloneNotSupportedException {
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DeepCopy2 t = (DeepCopy2)super.clone();
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t.c = new DeepCopy1();
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return t;
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}
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}
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public class DeepCopy {
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public static void main(String[] args) throws CloneNotSupportedException {
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DeepCopy2 t1 = new DeepCopy2();
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t1.a = 10;
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t1.b = 20;
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t1.c.x = 30;
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t1.c.y = 40;
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DeepCopy2 t3 = (DeepCopy2)t1.clone();
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t3.a = 100;
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t3.c.x = 300;
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System.out.println(t1.a + " " + t1.b + " " + t1.c.x + " " +t1.c.y);
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System.out.println(t3.a + " " + t3.b + " " + t3.c.x + " " + t3.c.y);
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}
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}

‎java-interview-questions/core-java/methods/FillInStackTraceMethod.java‎

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package methods;
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public class FillInStackTraceMethod {
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public static void main(String[] args) throws Throwable {
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FillInStackTraceMethod obj = new FillInStackTraceMethod();
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try {
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obj.showResult();
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} catch (Exception e) {
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System.out.println("Exception: "+e);
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e.printStackTrace();
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}
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}
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public void showResult() throws Throwable {
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}
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}

‎java-interview-questions/core-java/methods/PassByValue.java‎

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package methods;
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class Test {
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int x;
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Test(int i) { x = i; }
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Test() { x = 0; }
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}
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public class PassByValue {
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public static void main(String[] args) {
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Test t = new Test(10);
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change(t);
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System.out.println("New Value :" + t.x);
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}
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public static void change(Test t) {
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t.x = 10;
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}
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}

‎java-interview-questions/core-java/methods/ReturnListObjectClass.java‎

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package methods;
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import java.util.Arrays;
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import java.util.List;
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public class ReturnListObjectClass {
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public static List<Object> getDetails() {
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String name = "Pradeep";
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int age = 22;
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char gender = 'M';
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return Arrays.asList(name, age, gender);
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}
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public static void main(String[] args) {
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List<Object> person = getDetails();
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System.out.println(person);
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}
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}

‎java-interview-questions/core-java/methods/ShallowCopy.java‎

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package methods;
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/**
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* Whenever we use default implementation of clone method we get shallow copy of
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* object means it creates new instance and copies all the field of object to that
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* new instance and returns it as object type, we need to explicitly cast it back
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* to our original object. This is shallow copy of the object.
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*
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*/
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import java.util.ArrayList;
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class ShallowCopy1 {
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int x, y;
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}
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class ShallowCopy2 implements Cloneable {
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int a, b;
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ShallowCopy1 c = new ShallowCopy1();
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public Object clone() throws CloneNotSupportedException {
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return super.clone();
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}
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}
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public class ShallowCopy {
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public static void main(String[] args) throws CloneNotSupportedException {
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ShallowCopy2 t1 = new ShallowCopy2();
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t1.a = 10;
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t1.b = 20;
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t1.c.x = 30;
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t1.c.y = 40;
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ShallowCopy2 t2 = (ShallowCopy2)t1.clone();
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t2.a = 100;
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t2.c.x = 300;
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System.out.println(t1.a + " " + t1.b + " " + t1.c.x + " " + t1.c.y);
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System.out.println(t2.a + " " + t2.b + " " + t2.c.x + " " +t2.c.y);
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}
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}

‎java-interview-questions/core-java/multithreading/CallableExample.java‎

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package multithreading;
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import java.util.Random;
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import java.util.concurrent.Callable;
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import java.util.concurrent.FutureTask;
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public class CallableExample implements Callable {
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public Object call() throws Exception {
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Random generator = new Random();
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Integer randomNumber = generator.nextInt(5);
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Thread.sleep(randomNumber * 100);
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return randomNumber;
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}
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public static void main(String args[]) throws Exception {
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FutureTask[] randomNumberTasks = new FutureTask[5];
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for(int i = 0; i < 5; i++) {
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Callable callable = new CallableExample();
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randomNumberTasks[i] = new FutureTask(callable);
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Thread t = new Thread(randomNumberTasks[i]);
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t.start();
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}
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for(int i = 0; i < 5; i++){
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System.out.println("FutureTask: "+randomNumberTasks[i].get());
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}
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}
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}
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‎java-interview-questions/core-java/multithreading/CountDownLatchExample.java‎

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package multithreading;
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import java.util.concurrent.CountDownLatch;
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public class CountDownLatchExample {
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public static void main(String[] args) throws InterruptedException {
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CountDownLatch latch = new CountDownLatch(4);
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Worker first = new Worker(1000, latch, "WORKER-1");
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Worker second = new Worker(2000, latch, "WORKER-2");
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Worker third = new Worker(3000, latch, "WORKER-3");
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Worker fourth = new Worker(4000, latch, "WORKER-4");
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first.start();
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second.start();
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third.start();
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fourth.start();
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latch.wait(); // The main task waits for four threads
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System.out.println(Thread.currentThread().getName() + " has finised");
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}
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}
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class Worker extends Thread {
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private int delay;
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private CountDownLatch latch;
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public Worker(int delay, CountDownLatch latch, String name) {
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super(name);
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this.delay = delay;
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this.latch = latch;
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}
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@Override
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public void run() {
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try {
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Thread.sleep(delay);
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latch.countDown();
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System.out.println(Thread.currentThread().getName() + " finished");
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} catch (Exception e) {
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e.printStackTrace();
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}
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}
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}

‎java-interview-questions/core-java/multithreading/DaemonThread.java‎

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package multithreading;
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public class DaemonThread extends Thread {
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public DaemonThread(String name) {
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super(name);
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}
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public void run() {
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if(Thread.currentThread().isDaemon()) {
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System.out.println(getName() + " is Daemon thread");
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} else {
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System.out.println(getName() + " is User Thread" );
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}
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}
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public static void main(String[] args) {
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DaemonThread t1 = new DaemonThread("t1");
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DaemonThread t2 = new DaemonThread("t2");
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DaemonThread t3 = new DaemonThread("t3");
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t1.setDaemon(true);
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t1.start();
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t2.start();
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t3.setDaemon(true);
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t3.start();
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}
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}

‎java-interview-questions/core-java/multithreading/InterThreadCommunication.java‎

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package multithreading;
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import java.util.Scanner;
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import java.util.*;
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public class InterThreadCommunication {
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public static void main(String[] args) throws InterruptedException {
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final PC pc = new PC();
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Thread t1 = new Thread(new Runnable() {
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@Override
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public void run() {
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try {
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pc.produce();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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});
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Thread t2 = new Thread(new Runnable() {
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@Override
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public void run() {
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try {
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pc.consume();
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} catch (InterruptedException e) {
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e.printStackTrace();
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}
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}
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});
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// Start both threads
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t1.start();
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t2.start();
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// t1 finishes before t2
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t1.join();
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t2.join();
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}
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public static class PC {
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public void produce() throws InterruptedException {
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// Synchronized block ensure only one thread running at a time
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synchronized(this) {
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System.out.println("Producer thread running");
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// release the lock on shared resource
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wait();
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System.out.println("Resumed");
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}
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}
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public void consume() throws InterruptedException {
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Thread.sleep(1000);
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Scanner s = new Scanner(System.in);
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synchronized(this) {
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System.out.println("Waiting for return key");
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s.nextLine();
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System.out.println("Return key pressed");
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notify();
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Thread.sleep(2000);
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}
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}
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}
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}

‎java-interview-questions/core-java/multithreading/JoinExample.java‎

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package multithreading;
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public class JoinExample implements Runnable {
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public void run() {
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Thread t = Thread.currentThread();
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System.out.println("Current Thread: " + t.getName());
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System.out.println("Is Alive? " + t.isAlive());
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}
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public static void main(String[] args) {
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Thread t = new Thread(new JoinExample());
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t.start();
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try {
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// Waits for 1000ms this thread to die
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t.join(1000);
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} catch (Exception e) {
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System.out.print(e);
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}
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System.out.println("Current Thread: " + t.getName());
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System.out.println("Is Alive? " + t.isAlive());
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}
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}

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