Constructor-
Definition-
Constructor is used to construct the objects.
-It initialize default or given values to object.
Syntax-
modifiers ClassName(parameters) {
//Constructor body
}
Rules of creation-
1- Constructor Name should be same as class name.
Rules of implementation-
1- constructor always should be followed by new keyword.
Types of constructor-
1- Non Parameterized constructor
2– Parameterized constructor
1- Non Parameterized
(i)Default constructor-
Only when no constructor is created in class, compiler adds default constructor.
Syntax- created by compiler in compiled code- constructorName(){
}
(ii) Manual Constructor-
Constructor created with no parameters.
It can have statements in constructor body.
Syntax - modifiers constructorName(){
Statements
}
2- Parameterized Constructor-
Constructor created with parameters.
It also can have statements in constructor body.
Syntax- modifiers constructotName(parameters) {
Statements
}
Methods-
method is a set of statements to perform operations
Syntax –
Modifiers returnType methodName(parameters) {
//statements
}
Note- ReturnType= datatypes + void
code samples are here
1-Program to use default constructor(automatic creation)-
package constructors3;
public class Const1 {
public static void main(String[] args) {
Const1 c1 = new Const1();
}
}
2-Program to create manual constructor which prints “a” and then use this manual constructor –
package constructors3;
public class Const2 {
public Const2() {
System.out.println("a");
}
public static void main(String[] args) {
Const2 c1 = new Const2();
}
}
3-Program to create parameterized constructor which takes String s as parameter and then use it by giving “Got it” as argument –
package constructors3;
public class Const3 {
public Const3(String s) {
System.out.println(s);
}
public static void main(String[] args) {
Const3 name = new Const3("Got it");
}
}
4-Program to create more than 1 constructor with different parameters then use all constructors by giving arguments.
package constructors3;
public class Const4 {
public Const4(int i,String a) {
System.out.println(i+a);
}
public Const4(String a,int i) {
System.out.println(a+i);
}
public Const4(double h,char o) {
System.out.println(h+" "+o);
}
public static void main(String[] args) {
Const4 c = new Const4(6, "deep");
Const4 c1 = new Const4(65.45d, 'p');
Const4 c2 = new Const4("kaushik",10);
}
}
