Java Training in Chennai – Basics – Learning – Part – IV
This blog explains about Java Training in Chennai – Basics – Learning – Part – IV. Some of them are discussed below .
We have already about some programming in the previous blogs , Java Training in Chennai – Basics – Learning – Part – I , II & III
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Chapter 7: Inheritance
Question 1:
class Base {
public void show() {
System.out.println(“Base::show() called”);
}
}
class Derived extends Base {
public void show() {
System.out.println(“Derived::show() called”);
}
}
public class Main {
public static void main(String[] args) {
Base b = new Derived();;
b.show();
}
}
final public void show() {
System.out.println(“Base::show() called”);
}
}
Question 2:
class Base {
final public void show() {
System.out.println(“Base::show() called”);
}
}
class Derived extends Base {
public void show() {
System.out.println(“Derived::show() called”);
}
}
class Main {
public static void main(String[] args) {
Base b = new Derived();;
b.show();
}
}
Question 3:
class Base {
public static void show() {
System.out.println(“Base::show() called”);
}
}
class Derived extends Base {
public static void show() {
System.out.println(“Derived::show() called”);
}
}
class Main {
public static void main(String[] args) {
Base b = new Derived();;
b.show();
}
}
Question 4:
class A
{
int b = 50;
}
class B extends A
{
int b = 20;
}
public class MainClass
{
public static void main(String[] args)
{
A a = new B();
System.out.println(a.b);
}
}
Question 5:
class Base{
public Base(){
System.out.print(“Base”);
}
}
public class Derived extends Base{
public Derived(){
this(“Examveda”);
System.out.print(“Derived”);
}
public Derived(String s){
System.out.print(s);
}
public static void main(String[] args){
new Derived();
}
}
Question 6:
abstract class C1{
public C1(){
System.out.print(1);
}
}
class C2 extends C1{
public C2(){
System.out.print(2);
}
}
class C3 extends C2{
public C3(){
System.out.println(3);
}
}
public class Test{
public static void main(String[] a){
new C3();
}
}
public class Test
{
public static void main(String[] args)
{
int i = 100;
long l = i;
float f = l;
System.out.println(“Int value “+i);
System.out.println(“Long value “+l);
System.out.println(“Float value “+f);
}
}
public class Test
{
public static void main(String[] args)
{
double d = 100.04;
long l = (long)d;
int i = (int)l;
System.out.println(“Double value “+d);
System.out.println(“Long value “+l);
System.out.println(“Int value “+i);
}
}
class IntToByteConversion
{
public static void main(String arg[])
{
int a = 350;
byte b;
b = (byte) a;
System.out.println(“b = ” + b );
}
}
class DatatypeCasting
{
public static void main(String arg[])
{
byte b;
int i = 81;
double d = 323.142;
float f = 72.38f;
char c = ‘A’;
c = (char) i;
System.out.println(“i = ” + i + ” c = ” + c);
i = (int) d; // LINE A
System.out.println(“d = ” + d + ” i = ” + i); // LINE B
i = (int) f; // LINE C
System.out.println(“f = ” + f + ” i = ” + i); // LINE D
b = (byte) d;
System.out.println(“d = ” + d + ” b = ” + b);
}
}
Verify the Output
class Vehicle
{
int maxSpeed = 120;
}
/* sub class Car extending vehicle */
class Car extends Vehicle
{
int maxSpeed = 180;
void display()
{
/* print maxSpeed of base class (vehicle) */
System.out.println(“Maximum Speed: ” + super.maxSpeed);
}
}
/* Driver program to test */
class Test
{
public static void main(String[] args)
{
Car small = new Car();
small.display();
}
}
What is the output.
/* Base class Person */
class Person
{
void message()
{
System.out.println(“This is person class”);
}
}
/* Subclass Student */
class Student extends Person
{
void message()
{
System.out.println(“This is student class”);
}
// Note that display() is only in Student class
void display()
{
// will invoke or call current class message() method
message();
// will invoke or call parent class message() method
super.message();
}
}
/* Driver program to test */
class Test
{
public static void main(String args[])
{
Student s = new Student();
// calling display() of Student
s.display();
}
}
Check the output
/* superclass Person */
class Person
{
Person()
{
System.out.println(“Person class Constructor”);
}
}
/* subclass Student extending the Person class */
class Student extends Person
{
Student()
{
// invoke or call parent class constructor
super();
System.out.println(“Student class Constructor”);
}
}
/* Driver program to test*/
class Test
{
public static void main(String[] args)
{
Student s = new Student();
}
}
Verify the output for the below classes:
public Class SuperDemo{
int a,b;
}
public Class Subdemo extends SuperDemo{
int a,b;
void disply(){
System.out.println(a);
System.out.println(b);
super.a=10;
super.b=20;
System.out.println(super.a);
System.out.println(super.b);
}
public static void main (String args[]) {
Subdemo obj= new Subdemo();
obj.a=1;
obj.b=2;
obj.disply();
}
}
Verify the output for the below coding:
public Class SuperDemo{
int a,b;
public void show() {
System.out.println(a);
System.out.println(b);
}
}
public Class Subdemo extends SuperDemo{
int a,b;
void disply(){
System.out.println(a);
System.out.println(b);
super.a=10;
super.b=20;
super.show();
}
public static void main (String args[]) {
Subdemo obj= new Subdemo();
obj.a=1;
obj.b=2;
obj.disply();
}
}
Verify the output:
public Class SuperDemo{
int a,b;
SuperDemo(int x, int y){
a=x;
b=y
System.out.println(“Super class constructor called “);
}
}
public Class Subdemo extends SuperDemo{
int a,b;
SubDemo(int x, int y){
super(10,20);
a=x;
b=y
System.out.println(“Sub class constructor called “);
}
public static void main (String args[]) {
Subdemo obj= new Subdemo(1,2);
}
}
Verify the output:
public class ThisDemo {
int a, b;
ThisDemo(int a, int b){
a=a;
b=b;
}
public static void main(String[] args){
ThisDemo obj= new ThisDemo(1,2);
System.out.println(obj.a);
System.out.println(obj.b);
}
public class ThisDemo {
int a, b;
ThisDemo(int a, int b){
this.a=a;
this.b=b;
}
public static void main(String[] args){
ThisDemo obj= new ThisDemo(1,2);
System.out.println(obj.a);
System.out.println(obj.b);
}
}
public class ThisDemo {
int a, b;
ThisDemo(){
System.out.println(“Default constructor called”);
}
ThisDemo(int a, int b){
this();
this.a=a;
this.b=b;
}
public static void main(String[] args){
ThisDemo obj= new ThisDemo(1,2);
System.out.println(obj.a);
System.out.println(obj.b);
}
}
public class Test{
int a, b;
Test(int a, int b){
this.a=a;
this.b=b;
}
void show(){
System.out.println(“Show() method called”);
}
void print(){
this.show();
System.out.println(a);
System.out.println(b);
}
public static void main(String[] args){
Test obj= new Test(1,2);
obj.print()
}
}
Guess the output:
public class InheritanceTest
{
public static void main(String[] args)
{
Parent c = new Child();
c.doSomething();
}
}
class Parent
{
public void doSomething()
{
System.err.println(“Parent called”);
}
}
class Child extends Parent
{
public void doSomething()
{
System.err.println(“Child called”);
}
}
What is the output?
public class InheritanceTest
{
public static void main(String[] args)
{
Parent c = new Child();
}
}
class Parent
{
public Parent()
{
System.err.println(“Parent called”);
}
}
class Child extends Parent
{
public Child()
{
System.err.println(“Child called”);
}
}
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Chapter 8: Interfaces and Abstract Classes
Predict the output of the following program.
abstract class demo
{
public int a;
demo()
{
a = 10;
}
abstract public void set();
abstract final public void get();
}
class Test extends demo
{
public void set(int a)
{
this.a = a;
}
final public void get()
{
System.out.println(“a = ” + a);
}
public static void main(String[] args)
{
Test obj = new Test();
obj.set(20);
obj.get();
}
}
What is the output of this program?
interface calculate {
void cal(int item);
}
class display implements calculate {
int x;
public void cal(int item) {
x = item * item;
}
}
class interfaces {
public static void main(String args[]) {
display arr = new display;
arr.x = 0;
arr.cal(2);
System.out.print(arr.x);
}
}
What is the output of this program?
interface calculate {
int VAR = 0;
void cal(int item);
}
class display implements calculate {
int x;
public void cal(int item) {
if (item<2)
x = VAR;
else
x = item * item;
}
}
class interfaces {
public static void main(String args[]) {
display[] arr=new display[3];
for(int i=0;i<3;i++)
arr[i]=new display();
arr[0].cal(0);
arr[1].cal(1);
arr[2].cal(2);
System.out.print(arr[0].x+” ” + arr[1].x + ” ” + arr[2].x);
}
}
What should be done to compile the code successfully?
interface IBeingZeroStudent
{
double getPercentageMarks();
String getName();
int getAge();
}
class BeingZeroStudent implements IBeingZeroStudent
{
public String getName()
{
return “BeingZeroStudent”;
}
public int getAge()
{
return 20;
}
}
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References:
https://payilagam.com/blogs/java-training-in-chennai-basics-learning-part-i/
https://payilagam.com/blogs/java-training-in-chennai-basics-learning-part-ii/
https://payilagam.com/blogs/java-training-in-chennai-basics-learning-part-iii/
COURTESY :
www.proprofs.com, meritcampus.com, www.geeksforgeeks.org,
www.f5java.com, dzone.com, www.examveda.com, beingzero.in/,
scjptest.com, www.gocertify.com, web.cs.iastate.edu,
www.sanfoundry.com, https://codingpuzzles.com