Constructors:

It is an instance method that usually has the same name as the class and can be used to set the value of members of the object.(either default or user defined values).
java allows themselves to create the object in which constructor helps in automatic initialize.
constructor not have return type and not void because the implicit return type of class constructor is a return type itself.

Example:

box(){
System.out.println("Constructing box");
width=20;
height=20;
depth=20;
}

since the constructor gives all boxes the same value 10 by 10 by 10 in mybox1 and mybox2 as having same dimensions & volume.
the default constructor automatically construct the class values as zero,null,false.It works for simple classes.but for large class we want to define the own constructor.

parameterized constructor;

This keyword: In these operation use of this is redundant but it is correct in executing like in previous version.

Instance variable hiding:

Including formal parameters overlap the local variable as same as the name of the class instance variable.
However when local variable has the same name as instance variable then the local variable hides the instance variable.

Syntax:

   box(double width,double height,double depth){

   this.width = width;

   this.height = height;

   this.depth = depth;
   }

In these formal parameter and use of local variable can hides the variable which has the same name for clarity.

Garbage collection:

In c++ the dynamically allocated memory is used by the delete operator.
But in java it is deallocates the memory automatically.This technique is called Garbage collection.
When no reference to object in program,then memory of particular object exist is deallocated.

Finalize() methods:

You can define the specific action to be destroyed or reclaimed for garbage collection.
It implement by finalize()method.
Inside the finalize() method that we want to specify those actions that must be performed before it destroyed.

     protected void finalize(){

        //...finalization code here

         }

A stack class:

Constructors

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