Constructor,this Keyword,Packages...

Constructor:

Zero Argument constructor:

• A zero-argument constructor is a constructor that takes no parameters.

• You write it explicitly to set up default or custom values for an object.

Example:

class MyClass {
    // Zero-argument constructor
    MyClass() {
        System.out.println("Zero-argument constructor called");
    }
}

Default constructor:

• A default constructor is a constructor that Java provides automatically only if you don’t define any constructor in your class. It:
  • Takes no arguments.
  • Initializes object with default values (like 0, null, false, etc.).

Example:

public class Student {
    int id;
    String name;
}

// Java automatically provides a default constructor:
// Student() { }

This:

• This Keyword.

• The this keyword in Java refers to the current object in a method or constructor.

• This keyword is used to differentiate between local and global variable.

• When local variable names are the same as instance variables, this is used to differentiate

Example:

public class Student {
    String name;

    public Student(String name) {
        this.name = name; 
    }
}

Package:

In java packages means folder.

Why use packages?

• Avoid class name conflicts.

• Make code easier to maintain and understand.

create package:

package com.indianBank;


compile package:

javac -d . classname.java

Run package:

java filename