Core Java - JAVA DEVELOPMENT Training By Om Sir

(1)CLASS EXAMPLE FOR CREATING OBJECT & CALLING MEMBER VARIABLE & MEMBER FUNCTIONS.

public class Puppy
{

int puppyAge;

public Puppy(String name){
// This constructor has one parameter, name.
System.out.println("Passed Name is :" + name );
}
public void setAge( int age ){
puppyAge = age;
}

public int getAge( )
{
System.out.println("Puppy's age is :" + puppyAge );

return puppyAge;

}

public static void main(String []args)

{
/* Object creation */

Puppy myPuppy = new Puppy( "tommy" );

/* Call class method to set puppy's age */

myPuppy.setAge( 2 );

/* Call another class method to get puppy's age */

myPuppy.getAge( );

/* You can access instance variable as follows as well */

System.out.println("Variable Value :" + myPuppy.puppyAge );

}

}

Output:

D:\>javac Puppy.java

D:\>java Puppy
Passed Name is :tommy
Puppy's age is :2
Variable Value :2

(2)ARRAY EXAMPLE:

class arrayexample

{

public static void main(String args[])

{

int a[]=new int[5]; //declaration and instantiation

a[0]=10; //initialization
a[1]=20;
a[2]=70;
a[3]=40;
a[4]=50;

//printing array

for(int i=0;i<a.length;i++) //length is the property of array

System.out.println(a[i]);

}

}

Output:

D:\>javac arrayexample.java

D:\>java arrayexample
10
20
70
40
50

(3)STRING EXAMPLE:

public class StringExample

{

public static void main(String args[])

{

String s1="java"; //creating string by java string literal

char ch[]={'s','t','r','i','n','g','s'};

String s2=new String(ch); //converting char array to string

String s3=new String("example"); //creating java string by new keyword

System.out.println(s1);

System.out.println(s2);

System.out.println(s3);

}

}

here is ouput :

D:\>set path="C:\Program Files (x86)\Java\jdk1.8.0_40\bin"

D:\>javac StringExample.java

D:\>java StringExample
java
strings
example

(4)JAVA INHERITANCE EXAMPLE:

save following code Programmer.java note:here is Employee is super class and Programmer is child class :

class Employee

{

float salary=40000;

}

class Programmer extends Employee

{

int bonus=10000;

public static void main(String args[])

{

Programmer p=new Programmer();

System.out.println("Programmer salary is:"+p.salary);

System.out.println("Bonus of Programmer is:"+p.bonus);

}

}

D:\>javac Programmer.java

D:\>java Programmer
Programmer salary is:40000.0
Bonus of Programmer is:10000

(5)JAVA INTERFACE:

(a)create interface and save following code as "Animal.java":

interface Animal {

public void eat();
public void travel();
}

Then complie it

D:\>javac Animal.java

(b) write code for a class that implements this interface and save it as "MammalInt.java":

public class MammalInt implements Animal{

public void eat(){
System.out.println("Mammal eats");
}

public void travel(){
System.out.println("Mammal travels");
}

public int noOfLegs(){
return 0;
}

public static void main(String args[]){
MammalInt m = new MammalInt();
m.eat();
m.travel();
}
}

Then run it:

D:\>javac MammalInt.java

D:\>java MammalInt
Mammal eats
Mammal travels

(6)PACKAGE EXAMPLE:

(a)package exampel in java:

first create a folder name abc:

(b)write coe for A.java :

package abc;

public class A

{

public void msg()

{

System.out.println("Hello");

}

}

(c)compile it :

D:\>javac A.java

then you will get bytecode file A.class

copy this file & paste it into abc folder.

(d)now import this class from abc folder example save following code by name B.java :

import abc.A; // here we are importing class A from package abc

class B{
public static void main(String args[]){
A obj = new A();
obj.msg();
}
}

now run it:

D:\>javac B.java

D:\>java B

Hello