Generic Constructor

This is an example of how to use a generic constructor of a class. In order to see how a generic constructor works we have created a class with a generic constructor and then created instances of the class to use its constructor.

• GenericClass class has a double field, val.
• It has a constructor using an object of T class that extends Number, sets its double field to the object’s double value, using doubleValue() API method of Number and returns the object.
• It has a method void value() that prints the double field of the class.
• We create a new instance of GenericClass with a given Integer object and another instance of GenericClass with a given Float object, and call values() method for both objects.
• In both cases the double value of the fields are returned.

Let’s take a look at the code snippet that follows:

package com.javacodegeeks.snippets.core;


class GenericClass {

    private double val;

    <T extends Number> GenericClass(T arg) {

  val = arg.doubleValue();
    }

    void values() {

  System.out.println("val: " + val);
    }
}

public class GenericConstructor {

    public static void main(String args[]) {


  GenericClass c1 = new GenericClass(100);

  GenericClass c2 = new GenericClass(123.5F);

  


  c1.values();

  c2.values();

 
    }
}

Output:

val: 100.0
val: 123.5

  
This was an example of how to use a generic constructor of a class in Java.