Java Constructor

Cited from the Book Java How to Program

Each class you declare can provide a special method called a constructor that can be used to initialize an object of a class when the object is created. In fact, Java requires a constructor call for every object that’s created. 

Keyword new requests memory from the system to store an object, then calls the corresponding class’s constructor to initialize the object. The call is indicated by the parentheses after the class name. A constructor must have the same name as the class.

By default, the compiler provides a default constructor with no parameters in any class that does not explicitly include a constructor. When a class has only the default constructor, its instance
variables are initialized to their default values.

When you declare a class, you can provide your own constructor to specify custom initialization for objects of your class.

An important difference between constructors and methods is that constructors cannot return values, so they cannot specify a return type (not even void). Normally, constructors are declared public. If a class does not include a constructor, the class’s instance variables are initialized to their default values. If you declare any constructors for a class, the Java compiler will not create a default constructor for that class.