Constructors and their usage

Key and important note on constructors

• Block of code executed whenever an object is created
• Constructor does not return any values
• Name of the Constructor  should be the class name.
• Compiler will call default/implicit constructor(java- library-if not defined any constructor block).
• Constructor will be called whenever an object is created.
• In real-time Constructor  is used to define variables or to initiate properties 

sample code for constructor:

public class constructorDemo {

public constructorDemo() {

System.out.println("i am in the constructor");

}

public void getData() {

System.out.println("i am the method");

}

public static void main(String[] args) {

// TODO Auto-generated method stub

constructorDemo obj = new constructorDemo();

// obj is created to call constructor (constructorDemo)

}

}

Parameterized constructor

public class constructorDemo {

public constructorDemo() {

System.out.println("i am in the constructor");

}

public constructorDemo(int a, int b) {

System.out.println("i am in the parametrized constructor");

int c = a + b;

System.out.println(c);

}

public constructorDemo(String str) {

System.out.println(str);

}

public void getData() {

System.out.println("i am the method");

}

public static void main(String[] args) {

// TODO Auto-generated method stub

constructorDemo obj = new constructorDemo(4, 5);

constructorDemo obj1 = new constructorDemo("Hello");

// obj is created to call constructor (constructorDemo)

}

}