Java constructor
What is a constructor?
§ Constructor in java special type of method that is used to initialize the object.
§ Constructor name must be same as its class
name.
§ Constructor
must have (no explicit return type)
Constructors are
two types:-
1.
Default
constructor
2.
Parameterized
constructor
Example:-
Class
Abc {
Abc a= new Abc();
}
Abc()- is a constructor
Example of default
constructor:--
Class ABC
{
//no parameter //no arguments
}
Example of Parameterized
constructor:--
Class ABC
{
ABC( int a,
int y, String z) { // its content argument
//body
}
}
Various senarious
in java constructor:
Case1:-- when no default constructor is provided.
Example:-- class
Test {
int x;
float y;
public static void
main(String args[]) {
Test t= new
Test();
System.out.println(t.x);
System.out.println(t.y);
}
}
Case2:-- when no default constructor is provided by the user.
Use where user wants to
initialized the various with value other than java default values
Example:-- class
Test {
int x;
Test(); {
x= 12;
}
public static void
main(String args[]) {
Test t= new
Test();
System.out.println(t.x);
}
}
Case3:-- when no Parameterized constructor is provided by the user(constructor with argument).
Example:-- class
Test {
Test(int a,
String b); {
x= a;
y=b;
}
public static void
main(String args[]) {
Test t= new
Test(12, “programming khata”);
System.out.println(t.x);
System.out.println(t.y);
}
}
Case4:-- constructor overloading (exactly similar to method overloading)
Example:-- class Test {
Test(int a, String b); {
x= a;
y=b;
}
public static void main(String args[]) {
Test t= new Test(12, “programming khata”); // this is Parameterized
Test t= new Test(); //this is default
System.out.println(t.x);
System.out.println(t.y);
}
}
Q.1 what will happen if only Parameterized is
declared in the program and you try to
call the default constructor?
Ans- ERROR
Q.2 can you define a method with the same name as the constructor?
Ans:- Yes it is possible.
0 Comments