A class is nothing but a blueprint or a template for creating different objects which defines its properties and behaviors. Java class objects exhibit the properties and behaviors defined by its class. A class can contain fields and methods to describe the behavior of an object.
A. Syntax for a Class in Java
ClassName.java
public class ClassName {
// Declare Variables and Method
public ClassName() {
// Initialise values to Variables
}
public void functionName() {
// Write Code Inside Method
}
}
class MainClassName {
public static void main(String args[]) {
/*
*
* Create Object to ClassName class
*
* Access Variables and Methods inside ClassName class
*
*/
}
}
B. Create a Class in Java
Class_Example_1.java
public class Class_Example_1 {
int a;
float b;
String str;
public Class_Example_1()
{
a = 10;
b = (float) 15.26;
str = "Java";
}
public void display()
{
System.out.println("The Integer Value is : "+a);
System.out.println("The Float Value is : "+b);
System.out.println("The String Value is : "+str);
}
}
class mainClass {
public static void main (String args[])
{
Class_Example_1 obj = new Class_Example_1();
obj.display();
}
}
Sample Output
The Integer Value is : 10
The Float Value is : 15.26
The String Value is : Java
C. Create More Classes in Java
Class_Example_2.java
public class Class_Example_2 {
void display1() {
System.out.println("This is Class - 1");
}
}
class Class2 {
void display2() {
System.out.println("This is Class - 2");
}
}
class Class3 {
void display3() {
System.out.println("This is Class - 3");
}
}
class MainClass {
public static void main(String[] args) {
Class_Example_2 obj1 = new Class_Example_2();
Class2 obj2 = new Class2();
Class3 obj3 = new Class3();
obj1.display1();
obj2.display2();
obj3.display3();
}
}
Sample Output
This is Class - 1
This is Class - 2
This is Class - 3
D. Create Nested Classes in Java
Class_Ex4.java
public class Class_Ex4 {
int a, b, c;
Class_Ex4() {
a = 10;
b = 20;
}
class InnerClass {
InnerClass() {
c = a +b;
}
void display() {
System.out.println("The Addition is : " + c);
}
}
void display() {
System.out.println("'A' is : " + a);
System.out.println("'B' is : " + b);
}
}
class MainClass {
public static void main(String args[]) {
Class_Ex4 obj1 = new Class_Ex4();
Class_Ex4.InnerClass obj2 = obj1.new InnerClass();
obj1.display();
obj2.display();
}
}
Sample Output
'A' is : 10
'B' is : 20
The Addition is : 30
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