Is there a way to instantiate abstract class

0 votes

Can we instantiate an abstract class?

abstract class my {
    public void mymethod() {

class poly {
    public static void main(String a[]) {
        my m = new my() {};

Here, I'm creating instance of my class and calling method of abstract class. Can anyone please explain this to me?

Dec 12, 2018 in Java by Rishabh
• 3,620 points

1 answer to this question.

0 votes

No, you are not creating the instance of your abstract class here. Rather you are creating an instance of an anonymous subclass of your abstract class. And then you are invoking the method on your abstract class reference pointing to subclass object.

This behaviour is clearly listed in JLS - Section # 15.9.1: -

If the class instance creation expression ends in a class body, then the class being instantiated is an anonymous class. Then:

  • If T denotes a class, then an anonymous direct subclass of the class named by T is declared. It is a compile-time error if the class denoted by T is a final class.
  • If T denotes an interface, then an anonymous direct subclass of Object that implements the interface named by T is declared.
  • In either case, the body of the subclass is the ClassBody given in the class instance creation expression.
  • The class being instantiated is the anonymous subclass.

Emphasis mine.

Also, in JLS - Section # 12.5, you can read about the Object Creation Process. I'll quote one statement from that here: -

Whenever a new class instance is created, memory space is allocated for it with room for all the instance variables declared in the class type and all the instance variables declared in each superclass of the class type, including all the instance variables that may be hidden.

Just before a reference to the newly created object is returned as the result, the indicated constructor is processed to initialize the new object using the following procedure:

You can read about the complete procedure on the link I provided.

To practically see that the class being instantiated is an Anonymous SubClass, you just need to compile both your classes. Suppose you put those classes in two different files:

abstract class My {
    public void myMethod() {

class Poly extends My {
    public static void main(String a[]) {
        My m = new My() {};

Now, compile both your source files:


Now in the directory where you compiled the source code, you will see the following class files:

Poly$1.class  // Class file corresponding to anonymous subclass

See that class - Poly$1.class. It's the class file created by the compiler corresponding to the anonymous subclass you instantiated using the below code:

new My() {};

So, it's clear that there is a different class being instantiated. It's just that, that class is given a name only after compilation by the compiler.

In general, all the anonymous subclasses in your class will be named in this fashion:

Poly$1.class, Poly$2.class, Poly$3.class, ... so on

Those numbers denote the order in which those anonymous classes appear in the enclosing class.

answered Dec 12, 2018 by Sushmita
• 6,910 points

Related Questions In Java

0 votes
1 answer

Is there a way to mask the password from java user input that comes from Scanner class and System.out.Println()?

You can use the console class to do so. ...READ MORE

answered May 27, 2019 in Java by Omkar
• 69,230 points
0 votes
2 answers

what is the best way to convert an ArrayList to a String

You could probably use the Joiner class ...READ MORE

answered Aug 19, 2019 in Java by Sirajul
• 59,230 points
0 votes
1 answer

What is the simplest way to read JSON from a URL in java

Read json from url use url.openStream() and read contents ...READ MORE

answered Jun 13, 2018 in Java by samarth295
• 2,220 points
+1 vote
2 answers

Is there a code to find 64-bit JVM or 32-bit JVM (from within a program)?

Do I need to understand the difference ...READ MORE

answered Jun 11, 2019 in Java by Jim
• 810 points
0 votes
1 answer

Can Abstract Class have a Constructor?

Yes, an abstract class can have a ...READ MORE

answered May 11, 2018 in Java by sharth
• 3,370 points
0 votes
2 answers

Determining Class of an Object in Java

You can use: Object instance = new SomeClass(); instance.getClass().getName(); ...READ MORE

answered Nov 26, 2018 in Java by Sushmita
• 6,910 points
0 votes
1 answer

Decompiling Java Class Files

There are a few decompilers out there... ...READ MORE

answered Jun 1, 2018 in Java by Rishabh
• 3,620 points
0 votes
1 answer

What is abstract class in java?

A class that is declared with abstract ...READ MORE

answered Jun 11, 2018 in Java by Daisy
• 8,120 points
0 votes
3 answers

How to check whether a string is empty or not? Is there a function for this?

str != null && str.length() != 0 alternatively str ...READ MORE

answered Sep 11, 2018 in Java by Sushmita
• 6,910 points
0 votes
2 answers

Is there a destructor in Java?

try (BufferedReader br = new BufferedReader(new FileReader(path))) ...READ MORE

answered Sep 4, 2018 in Java by Sushmita
• 6,910 points
webinar_success Thank you for registering Join Edureka Meetup community for 100+ Free Webinars each month JOIN MEETUP GROUP