Invocation of a constructor

The creation of new object is done by calling special methods called constructors.

Invocation of a constructor

Syntax:

new className(parameters)

• new is a predefined operator
• className(parameters) is the signature of a special method called constructor. The name of a constructor coincides with the name of the class to which it belongs.

A certain class can have many constructors, which differ in the number and/or types of their parameters (overloading of constructors).

Semantics:

The invocation of a constructor constructs a new object of the class to which the constructor belong and returns a reference to the created object. The object is constructed by making use of the parameters passed to the constructor.

Example:

new String("test")

• new is the predefined operator
• String(String s) is a constructor of the class String

The expression constructs a new object of the class String that is equal to the string denoted by "test". The reference to such an object is returned by the expression.

Example:

public class Hello {
  public static void main(String[] args) {
    String s = new String("hello world");
    System.out.println(s);
  }
}

Note that:

• the invocation of the constructor new String("hello world") creates a new object that is an instance of String and that represents the string "hello world"
• the reference to such an object is assigned to the variable s
• the value of the object denoted by s (i.e., "hello world") is printed.