Constructor
Constructor is a java features, it can be used to
constructor objects.
The role of the Constructor in Object creation is to provide
initial value inside the object.
In java applications, constructors are executed exactly at
the time and creating object, not before creating object and not after creating
objects.
In java applications, we are able to utilize constructors to
provide initialization for class level variables.
Constructor name must be same at the respective class name.
Constructors are not having return types.
Constructors are not allowing the access modifiers like
static, final, abstractor,…….
Constructor are able to allow the access modifiers like
public, protected, <default> and private.
Constructors are able to allow “throws” keyword to bypass
exceptions from present constructor to caller.
Syntax:-
[Access_MOdifier] Class_Name([Param_List]) [throws
Exception_list]
{
-----Instructions-----
}
Note 1:-
If we provide a constructer in a class without the same name
of the class name then compiler will raise an error like “Invalid Method
declaration; return type required” because compiler will treat the provided
constructor as normal java method without return type.
Note 2:-
In java methods return type in mandatory
Note 3:-
In java Applications, constructors are not allowing return
types, if we provide return type to the constructors, then compiler will not
raise any error and JVM will provide any output. Because, the provided
constructor is converted as normal java method with the same class. If we
access this constructor like normal java method then the provide constructor
will executed like normal java method.
Ex code:-
class A
{
void
A()
{
System.out.println("A-Con");
}
}
class Test
{
public
static void main(String[] args)
{
A
a=new A();
a.A();
}
}
Output:-
A-Con
Note 4:-
In java application , constructors are not allowing the
access modifiers like static, final, abstractor,……..if we provide constructors
with the above specified access modifiers then compiler will raise an error
like “Modifier XXX not allowed here”.
Ex code:-
class A
{
static
A()
{
System.out.println("A-Con");
}
}
class Test
{
public
static void main(String[] args)
{
A
a=new A();
}
}
Status:- compiler error, modifiers is not
existed .
Note 5:-
In java applications, constructor are able to allows the
access modifiers like public, protected, <default> and private. If we
declare any constructor as private then the provided constructor is available
up to the respective class, it is not available to outside of the respective
class. If we want to create object for the respective class. Then we have to
access private constructor in the same class.
There are two types of the constructors in java .
1.
Default constructor
2.
User defined constructor
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