Constructor in Java

Constructor

• A special method that matches the name of the class and has no return type
• Constructors are executed when a new instance of the class is created (new Main()). This process is called instantiation, because it creates a new instance of the class.
• The method name and the class name should be exactly same (note that Java is case sensitive)

• Constructors can include parameters, like arrays, primitive types or generics. But cannot include var. The below constructor will not compile.

    class Main {
      public Main( var number ) {
  
      }
    }
  

• There can be multiple constructors in a class, provided that the constructor parameters are distinct.
• Declaring multiple constructors with different signatures is reffered to as constructor overloading.
• Every class in Java will have a constructor. If you didn't code it Java will include the default no-argument constructor automatically during compilation process.

• Private Constructor is a special constructor which is declared as private. Having private constructors prevents other classes from the class. It is generally used when the class has only static methods.

    class Main {
      private Main() {
  
      }
    }
  

• Classes with a private constructor can be extended only by an inner class, because an inner class is the only one that can access a private constructor by calling super().