all java programs

8/13/2019 All Java Programs

http://slidepdf.com/reader/full/all-java-programs 1/46



JAVA keywords:

+++++++++++++

Write a program to get an input from the user:-

=============================================

package string_packg;

import java.util.Scanner;

public class takeinputfromtheuser {

/**

* @param args

*/

public static void main(String[] args) {

int a;

// TODO Auto-generated method stub

Scanner obj = new Scanner(System.in);

System.out.println("Enter the value of integer");

a = obj.nextInt();

System.out.println(" You entered the integer " +a);

}

}

OUTPUT:-



======

Enter the value of integer

1

You entered the integer 1

NOTES:

======

iF YOU ARE GOING TO TAE A STRING AS AN INPUT THEN USE

s = obj.nextLine();

===========

IF YOU ARE ENTERING A FLOAT ValUE THEN USE

s = obj.nextFloat();

===========

CASTING:

=======

Implicit and Explicit.

1) IMPLICIT CASTING:-

===================


public class Casting {

/**

* @param args

*/




short short_ID = 12345;

int integer_ID = short_ID;// LOWER DATA TYPE VALUE IS BEING ASSIGNED TO A

VARIABLE OF HIGHER DATA TYPE

System.out.print(integer_ID);


}

}

2) EXPLICIT CASTING:-

====================


public class EXPLICITCASTING {

/**

* @param args

*/



int i = 123445;

short s = (short) i ;

System.out.print(s+"id");

}

}



output:

======

-7627id


public class EXPLICITCASTING {

/**

* @param args

*/



int i = 123445;

short s = i ; // (short) i is missing!

System.out.print(s+"id"); // '+' IS USED FOR CONCATENATION

}

}

OUTPUT:

======

ERROR!!!!

Type mismatch: cannot convert from int to short!

operators AND operands:



++++++++++++++++++++++

1)ARITHMETIC

Addn, Subn, Multpn, Divn, Modulo

2)UNARY ARITHMETIC:

==================

INCREMENT: ++

DECREMENT: --

<<<<PREFIX AND POSTFIX.

3)RELATIONAL:

============

==,!=,<,<=,>,>=.

4)LOGICAL:-

=========

cONDITIONAL AND && (BINARY OPERATOR) ( a k a sHORT CIRCUIT AND)

cONDITIONAL OR || ("")

and & (does the same function as double-and && in an if-else)

OR | (bitwise OPERATORS ,ARE THEY THERE???? BHAGAVANTHANIGE GOTTU!!!)

XOR ^

not !

USES &:

=======


public class LOGICAL {



*/


int i= 234;

int j=235;

int k=300;

int l =299;

if ((i>j)&&(k>l))

System.out.print("TRUE");

else

System.out.print("falsE");


}

}

output:

======

falsE ( SAME O/P AS IN THE PREVIOUS CASE )

INCREMENT AND DECREMENT OPERATORS:

==================================


public class INCREMENTPOSTANDPRE {

/**

* @param args

*/


int i=7,j = 7;



int s,d;

s= i++ + i++ + i++;

System.out.print(s);

d= ++j + ++j + ++j;

System.out.print(d);


}

}

OUTPUT:

======

24 27

SWITCH CASE

============


public class Switchcases {

/**

* @param args

*/


switch(2*3+4+5)

{

case 1:



case 4: System.out.print(" Right Choice");

break;

default: System.out.print("WRONG");

break;

}


}

}

OUTPUT:

======

nter the value of integer

545565667


WRONG

OUTPUT:

=======

Enter the value of integer

4


Right Choice

FOR LOOP:

========




b=--i+--i+--i;

System.out.print(a);

System.out.print(b);


}

}

O/P:

===

24 24

Why do we go for while and do- while loop when we know that for loop is easier?

A: When we do no t know the no of iterations that have to be done we go for while or do while

loop

Difference between while and dop while loop ?

While checks the condition and then executes whereas do-while executes aleast once even though

the condition is not satisfied.

ARRAYS:

======

String parkingspace= {"Car111","Car 222"," car333"};

String parkingspace [5]; THIS IS INVALID

String [] s = new String [5];

array.length gives the no of elements in the array.

Array index always starts from zero.

-----------------------------------------------------------------------------------------------------------------------------------

Activity1:



==========

take input from the user for no of subjects and then find the average marks of the marks entered

for the no of subjects chosen.



import java.io.*;

public class CalculateaverageArray {

/**

* @param args

*/


Scanner objt = new Scanner(System.in);

int i,n , sum=0, temp;

System.out.print("Enter the no of elements in the array");

n= objt.nextInt();

System.out.print(" You have entered the no of elements in the array");

int []a = new int [n];

System.out.print("Enter the marks");

for ( i=0; i<n; i++)

{

a[i]= objt.nextInt();

temp = a[i];

sum= sum +temp;

}

System.out.print(sum/n);




}

}

OUTPUT:

=======

Enter the no of elements in the array 3

You have entered the no of elements in the arrayEnter the marks34

43

100

59

Array out of bound -TRYING TO STORE MORE ELEMENTS THAN THE ARRAY7 C AN ACCOMODATE.

mETHODS:-

========

Methods define the behavior of a class.

Class A

{

int a=20;

String name ="VIT";

Sum() // Method

{

s= 1+2+3+4+5;

Syso(s);----------------------------------> System.out.print( a+ " "+b); Here value of a is printed and then

value of b is printed after a space mark.

------------------------------------------> System.out.print( " " +a+b); Here value of a is printed followed by

b without space

------------------------------------------->System.out.print( a+b) this will sum up thwe values of a and b and

print it.



AREA OF A RECTANGLE- COMPUTE IN THE CLASS RECTANGLE AND DISPLAY IT IN THE CLASS THAT

CONTAINS THE MAIN FUNCTION:

----------------------------------------------------------------------------------------------------------------

==================================================================================

==============================

(A) package string_packg;


public class RECTANGLE

{ void entries()

{int l, b, area;


System.out.println("Enter the value of breadth");

b = obj.nextInt();

System.out.println("Enter the value of length");

l = obj.nextInt();

area = l* b;

System.out.print(" The area of the rectangle:" +area);

}

}

(B) package string_packg;

public class Mainer {

/**

* @param args

*/





RECTANGLE obj = new RECTANGLE();

obj.entries();

}

}

OUTPUT:-

======

Enter the value of breadth

2

Enter the value of length

3

The area of the rectangle:6

Area of a triangle

==================



public class Triangle {

int a,b,c,s; double area;

void Area()

{

System.out.print("Enter the dimensions of the triangle");


a= obj.nextInt();

b= obj.nextInt();

c= obj.nextInt();

if(a>b+c||b>c+a||c>b+a )

{

System.out.print("Triangle does not exist");



}

else

{s= (a+b+c)/2;

area= Math.sqrt(s*(s-a)*(s-b)*(s-c));

System.out.print("Area of the triangle is "+area);

}

}

}

InClassStaticMethodCall:

========================

package staticmethodinclasscall;

public class Class1 {


greet("Java teacher");

}

public static void greet(String someperson)

{System.out.println("Hello"+someperson+"!");

}

}

output:

++++++

HelloJava teacher!

PASSING BY VALUE:

=================

STRING ARGS[] of MAIN METHOD:



=============================

package staticmethodinclasscall;

public class StringArguments {


int j=0;

while (j<2)

{

System.out.println(args[j]);

j++;

}

}

}

CODE TO SHOW THAT STATIC BLOCK OF CODE GETS EXE4CUTED EVEN BEFORE THE MAIN

METHOD:(INITIALIZATION IS DIONE BEFORE STAIC BLK EXECUTION)

=================================================================================

package newpackage;

public class Statvaraccess {

public static int a=5;

public static int b;

static void display()



{

System.out.print("You just called a static method");

}

static{

b=a*8;

System.out.print(b);

System.out.print("this is the first satic block of code");

}

public void method()

{

System.out.print("this is not a static block");

}

static

{

System.out.print("This is the second static block of code");

}


Statvaraccess obj = new Statvaraccess();

System.out.println(Statvaraccess.a);-------->(2)

System.out.println(obj.b);-------->(1)

obj.method();

display();

}

OUTPUT:

40this is the first satic block of codeThis is the second static block of code5



40

this is not a static blockYou just called a static method

======

NOTES=||

======

(1) tHERE IS NO NECESSITY TO CREATE AN OBJECT TO ACCESS A STATIC VARIABLE INSIDE THE SAME

CLASS

IN LIEU IT CAN BE SIMPLY WRITTEN AS

System.out.println(b);

(2) ALSO, WE REQUIRE CLASSNAME.VARIABLE NAME ONLY WHEN WE TRY TIO ACCESS THE STAT VAR

IN SOME OTHER CK

CLASS.SO, WRITE IT DIRECTLY AS

System.out.println(a);

(3) static block of code is called even befor ethe main method is called.

FUNCTIONING O F A STATIC VARIABLE

=================================

package newpackage;

public class Animal {

static int animalcount=0;

public Animal()

{

animalcount+=1;

}




System.out.println(" The no of animals are"+""+animalcount);// note had the

variable animalcount BEEN NON-STATIC THEN WE NEED AN INSTANCE ( REFERENCE VARIABLE;

OBJECT)

new Animal();//---> When the JVM goes for garbage collection it actually looks for

objects without refernce variable so these 3 objects are chosen for garbage collection

new Animal();----^

new Animal();----|

System.out.println(" The no of animals are"+""+animalcount);

}

}

OUTPUT:

=======

The no of animals are0

The no of animals are3

THERE CAN ONLY BE ONE PUBLIC CLASS INSIDE A .jAVA FILE.and that has the same name as the dot

java file.

Extends

======= One class extending another

+++++++++++++++++++++++++++

package newpackage;

public class EXTENSION extends ClassExtends{



int s,t; // 2 non-static vars

public static void main(String[] args)

{

EXTENSION obj = new EXTENSION ();

/*instantiation: note here

to access the attributes and methods

of the PARENT class the object of

CHILD class

will suffice*/

obj.s =a+6;

obj.t= obj.b +5;

somemethod();

obj.somemethod();

/*WARNING: A static method of the parent class

+++++++ can be accessed simply by name

instead of creating an obj

to do the same*/

obj.met2();

}

}



class ClassExtends {

static int a=6; int b=7;// variable a is static and b NON-static

static void somemethod()// static method

{

System.out.print("Sample statement");

}

void met2()// NON-static mthd

{

System.out.print(" Yet another sample");

}

}

OUTPUT:

======

Sample statementSample statement Yet another sample

CANNOT ASSIGN A FINAL VARIABLE:

==================================

package newpackage;

public class FinalKeyWord {

final static int a =5;




//void bullshit() cannot create a method inside main method

++++++

{ a=9;// +ERROR+// Also, note that inside main you cannot declare static but FINAL

IS POSSIBLE.

++++++

}

}

}

FINAL METHOD:

============= THIS METHOD CAN BE INHERITED BUT CANNOT BE OVERriddEN.

OVERRIDE: SAME SIGNATURE BUT DIFFERENT RETURN TYPE.

OVERLOADING : DONE DURING COMPILE TIME

OVERRIDING AND POLYMORPHISM IS DONE DURING RUN TIME

OVERRIDING:

==========

package newpackage;

public class FInal extends B {

void Method1()

{

System.out.println("I am Lucky");

}


FInal obj = new FInal();

obj.Method1();// This object is going to call the method from the child class rather

than the parent class this is a property called overriding



}

}

class B

{

void Method1()

{

System.out.println("Let us override!!!");

}

}

output:

======

I am Lucky

Now see this magic !!!! Mudi Magix!!!!

package newpackage;+

public class FInal extends B {

void Method1()

{

System.out.println("I am Lucky");

}


FInal obj = new FInal();

obj.Method1();// YOU CANNOT BULLSHIT THIS TO OVERRIDE BECAUSE IT (method1)

IS MADE FINAL IN THE PARENT CLASS

// lOOK FOR IT YOURSELF HA HA HA !!! |



========================================

Source -----> Generate getters and setters.

Default value for string is null.

If you try to get before set then null value is returned .

The default value remains even after setting a new value.

When you set a value to the private variable using a set method then the object stores the newly set

value

but ther degfault values will remain in the blueprint of the class.effectively one cannot actually

change the

value of a private variable.

+++++++

CODE====

++++++++

package newpackage;

class GetterSetter {

private String name = "Akshay";

private String regNo = "10bec0004";

//Getter

public String getName()

{

return name;

}

public String getRegNo()

{

return regNo;

}

//sETTER



public void setName( String n)

{

name = n;

}

public void setRegNo(String r){

regNo=r;

}

//bsilfo-BYTE SHORT INT LONG FLOAT DOUBLE

}

public class Getter_Setter {


GetterSetter obj = new GetterSetter();

obj.setName("Bhargav");

obj.setRegNo("iitmee4556");

System.out.println(obj.getName());

System.out.println(obj.getRegNo());

}

}

output:

======

Bhargav

iitmee4556



long a = 123679891112141518// though the assigned no is withion the range of a long var. it throws

an error!!

[[[[[[[[[[[[[[[[[[[[[[[[[[[[[SOME BULLSHIT PROBLEM WITH THE COMPILER!!!!!]]]]]]]]]

sO,kindly excuse them for the inconvenience caused and do as follows( Not break the System!!)

long a = 123679891112141518L;//Now it recognizes this as a long variable and not as "int" as it had

done so previously.

Similarly for "float" write explicitly as "numer"f otherwise it considers it tp be double.

Inheritance allows you to extend an existing class to make a more splzed class.

Allows us to reuse the existing code.All classes in Java inherit from the object class.

constructors are not inherited'.

SUPER AND THIS:

==============

iNHERITANCE IS DESCRIOBED AS "IS-A" RELATIONSHIP. e.g; Dog is an Animal.

Aggregation HAS-A relationship.

Object class is the root class of asll classes.

Extends keyword is used for inhritance.

Multilevel inheritance:

=======================

Class A{

}

Class B extends A{ }

Class C extends B{} Here the class B is extended to C but not Class A as you may think.

Multiple inheritrance is not supported in Java:

===============================================

A child class having two or more parents is multiple inheritance.tO ACHIEVE THE SAME THEY USE

IONTERFACE IN JAVA.



AN EXAMPLE OF MULTILEVEL INHERITANCE:

====================================

package newpackage;


public class MultileV_inheritance extends passerine{


MultileV_inheritance obj = new MultileV_inheritance();

obj.bird();

obj.game_bird();

}

}

class Bird

{

int legs = 2;

static int wings =2;

void bird(){

System.out.println("Aves have many phyla ");

}

}

class passerine extends Bird

{

String game_birds;

Scanner gb = new Scanner(System.in);



void sample_passerine()

{

System.out.println("Sparrow is an example of a passerine bird");

}

void game_bird()

{ System.out.println("Enter the game_bird_instance");

game_birds= gb.nextLine();

System.out.println(game_birds);

}

}

OUTPUT:

======

Aves have many phyla

Enter the game_bird_instance

peacock

peacock

ORDER OF CONSTRUCTOR INVOCATION:

===============================

Notes annu refer madiri;;;;;;

SUPER MATTU THIS:

==================

Notes annu saha refer madiri

package newpackage;



public class DiffofThisAndSuper {


Animalia a = new Animalia();

a.eat();

Dog d = new Dog();

d.eat();

d. anotherEssen();

}

}

class Animalia

{

int i =90;

void eat()

{

System.out.println("animal:eat");

}

}

class Dog extends Animalia

{

int i= 45;

void eat()

{

System.out.println("dOGGY:ISST:dEUTSCH");

}

void anotherEssen()



{

this.eat();

super.eat();

System.out.println(this.i);

}

}

output:

++==++

animal:eat

dOGGY:ISST:dEUTSCH

dOGGY:ISST:dEUTSCH

animal:eat

45

Say, a class B extends class A , then , there exists automatically a super constructor in the default

constructor of class B -

But, if we explicitly write a parametrized constr. then the compiler does not create a default constr

and so ,there is no super() thus

creating a problem on extending class A.

Access modifier can be made broader when iot is narrow in the parent class.

A Jugglery of access modifiers:

==============================


class ConstrSuperThis extends MotherClass {

public void drive()// if this is private and the parent class mthd is public then error again because you

cannot modify the parent class access modifier

{



System.out.println("Hi! I am a KILLER whale!!??!!:) ");

}


ConstrSuperThis obj = new ConstrSuperThis ();

obj.drive();

MotherClass obj1= new MotherClass();

obj1.drive();//error

MotherClass obj2= new ConstrSuperThis();

obj2.drive(); // error parent class mthsd not visible

}

}

class MotherClass

{

private void drive()

{

System.out.println("Hi! I am a beluga whale!!");

}

}




class ConstrSuperThis extends MotherClass {

public void drive()

{

System.out.println("Hi! I am a KILLER whale!!??!!:) ");

}


ConstrSuperThis obj = new ConstrSuperThis ();

obj.drive();

MotherClass obj1= new MotherClass();

obj1.drive();

MotherClass obj2= new ConstrSuperThis();

obj2.drive();

}

}

class MotherClass

{

void drive()

{

System.out.println("Hi! I am a beluga whale!!");

}

}



o/p

===

Hi! I am a KILLER whale!!??!!:)

Hi! I am a beluga whale!!

Hi! I am a KILLER whale!!??!!:)

fOR I NTERFACE CLASSES WHEN WE PLAN TO IMPLEMENT SOME OF THE METHIODS OF THE

INTERFACE CLASS IN

THE NEXT CLASS TRHEN IT should BE DONE FULLY IN THAT CLASS.

ABSTRACT CLASS CANNOT BE INSTANTIATED.

iF WE TRY TO IMPLEMENT THE METHOD OF AN ABSTRACT CLASS IN THE NEXT CLASS AND SOMEMETHOD OF THE PARENT ABSTR CLASS IS STILL UNIMPLEMENTED THEN THE CHILDCLASS IS ONCE

AGAIN ABSTR.

oH! AN INTERFACE CLASS IS A PURE ABSTRACT CLASS

INTERFACE VARIABLES ARE BY DEFAULT PUBLIC STATIC FINAL.

==================================================================================

==================================================================================

====================

+++++++++++++++++++***************************************************************

++++++++++++++++++++++++++++++++++++++++++***********************************+++++

++++++++++++++++++++

JUNIT TESTING:

=\=*-+/-**/+*-


public class JunitTesting {

int l;

int m;

public JunitTesting ()

{



obj.mul(a, b);

}

}


import junit.framework.TestCase;

public class JunitTestingTest extends TestCase {

public JunitTesting v;

protected void setUp() throws Exception {

JunitTesting v = new JunitTesting();

v.l=5;

v.m= 9;

}

public void testAdd() {

assertEquals("Sorry valyue does not match",14,v.add(v.l,v.m));// 14 is the expected

value.

}// a.l and a.m are actual values

/* public void testSub() {

fail("Not yet implemented");

}

public void testMul() {

fail("Not yet implemented");

}*/



}

TRY CATCH FINALLY:

==================


public class TryAndCatch_Without {


int a=10;

int b=5;

int c=5;

int x,y;

try{

x=a/(b-c);

}catch(ArithmeticException ex)

{

System.out.println("Divide by zero");

}

y=a/(b+c);

System.out.println("y="+ y);

}

}

O/P:

===



Divide by zero

y=1

NESTED TRY CATCH:

================


import java.util.InputMismatchException;

public class NestedTryPrint {


try

{

System.out.println("Outer Try block atarts");

try{

System.out.println("Inner Try block starts");

int res=5/0;

}catch(InputMismatchException e){

System.out.println("InputMismatchException caught");/*HERE THERE IS NO CATCH BLOCK

THAT CATCHES ARITHMETIC EXCEPTION SO IT GOES TO INNER FINAL OF FINALLY

}finally

{

System.out.println("inner final");

}}catch(ArithmeticException e)

{System.out.println("Arithmetic exception caught");



} finally

{

System.out.println("Outer finally");

}

}

}

O/P:

====

Outer Try block atarts

Inner Try block starts

inner final

Arithmetic exception caught

Outer finally

never goes to inner try block becos it doesn ot get a chance

==================================================================


import java.util.InputMismatchException;

public class NestedTryPrint {


try

{



System.out.println("Outer Try block atarts");

int R= 6/0;

try{

System.out.println("Inner Try block starts");

int res=5/0;

}catch(InputMismatchException e){

System.out.println("InputMismatchException caught");

}finally

{

System.out.println("inner final");

}}catch(ArithmeticException e)

{System.out.println("Arithmetic exception caught");

} finally

{

System.out.println("Outer finally");

}

}

}

o/p:

====

Outer Try block atarts

Arithmetic exception caught

Outer finally

oops concepts:

============



Classes

Encapsulation

Inheritance

Association(GENLN, SPL.N && COMPOSITION AND AGGREGATION)

Interface Interface a{}

Implemet the methods in as ubclass as sollows

ClASS B IMPLEMENTS A

{

}AND NOTE THAT THE MTD IMPL SHUD BE COMPLETE.

Polymorphism( METHIDS CAN BE OVERLOADED AND OVERRIDDEN)

all java programs

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