Java constructors

Java constructors

Constructors in java are methods that are used to create new objects.They provide data to the object.
Note:

  • Constructors have no return type.
  • They are created using class name.
There are two types of Java Constructors.
  • No argument or default constructor.
  • Constructor with parameters.

Simple Java Default Constructor

public class Student {
    
    Student()
    {
    System.out.println("A new Student created");
    }
    public static void main(String args[])
    {
    Student s =new Student();
    }
    
}



Default constructor will provide null values or default to object

Example

public class Student {
    String name;
    int studentID;
    
   void showDetails()
   {
        System.out.println("Student name is " +name);
         System.out.println("Student ID  is " +studentID);
   }
    public static void main(String args[])
    {
    Student s =new Student();
    s.showDetails();
    Student s2=new Student();
    s2.showDetails();
   
    }
    
}


Parameterized  java constructor

A constructor with variables is called a parameterized constructors.They are used to give different values to object distinct.

Example:

public class Student {
    String name;
    int studentID;
    
    Student(String s,int id)
    {
        name=s;
        studentID=id;
    }
    
   void showDetails()
   {
        System.out.println("Student name is " +name);
         System.out.println("Student ID  is " +studentID);
   }
    public static void main(String args[])
    {
    Student s =new Student("Eric Mutua",222221);
    s.showDetails();
    Student s2=new Student("Jane Kate",232222);
    s2.showDetails();
   
    }
    
}


Output:
Student name is Eric Mutua
Student ID  is 222221
Student name is Jane Kate
Student ID  is 232222
BUILD SUCCESSFUL (total time: 0 seconds)

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