"Cannot subclass the final class" error, but the class is not final

Question

Here is my code:

package basic;

public abstract class Entity {}

package characters;

import basic.Entity;

public abstract class Character extends Entity {}

package player;

public class Player extends Character {}

I am getting the

The type Player cannot subclass the final class Character.

but I checked a million times and I am yet to use final all but ONCE in my project. What gives?

The answer is already given. Here's a tip how to find it out using your IDE (e.g. Eclipse). Place the mouse over the ´Character´ word, and it'll show you that it's `java.lang.Character` and not `characters.Character`. — Ralf Kleberhoff, Dec 14 '18 at 17:14

score 93 · Accepted Answer · answered Dec 14 '18 at 12:29

93

You are extending java.lang.Character (which does not need an import, as it comes from java.lang).

Insert import characters.Character into your Player code.

Reference: using package members:

For convenience, the Java compiler automatically imports two entire packages for each source file: (1) the java.lang package and (2) the current package (the package for the current file).

answered Dec 14 '18 at 12:29

Adam Kotwasinski

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Instead, rename the custom `Character` class. – chrylis -cautiouslyoptimistic- Dec 15 '18 at 07:14

score 17 · Answer 2 · answered Dec 14 '18 at 12:30

17

Character is a class of java.lang (the wrapper class of "char"). you have to import characters.Character in your Player class

package player;
import characters.Character

public class Player extends Character {

}

answered Dec 14 '18 at 12:30

Chris

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A better suggestion would be to avoid doubling the names of default library classes in your code-base altogether. Treat "Character" just as you would the keyword "char" since that's what it stands in for anyhow. I'd say rename the "Character" class to "Avatar", "Entity", "Person" or something else that won't cause any confusion with existing default classes. – Darrel Hoffman Dec 14 '18 at 18:39

Andrew Tobilko · Answer 3 · 2018-12-15T09:02:18.387

In this case, I strongly recommend using the fully qualified name of the Character class in the extends clause.

public class Player extends characters.Character {}

Experienced Java developers know that java.lang.Character is final and can't thereby be extended. By writing class Player extends Character, you would probably make them nonplussed.

Every compilation unit implicitly imports every public type name declared in the predefined package java.lang, as if the declaration import java.lang.*; appeared at the beginning of each compilation unit immediately after any package declaration. As a result, the names of all those types are available as simple names in every compilation unit.

^{Java 11 Specification > 7. Packages and Modules > 7.3. Compilation Units}

Of course, it would be more reasonable to pick up a name that doesn't collide with the classes from the standard java.lang package (like Person, or GameCharacter).

score 7 · Answer 4 · edited Dec 14 '18 at 13:43

7

Character is a final class as defined in Java Docs:

public final class Character
extends Object
implements Serializable, Comparable<Character>

so it cannot be sub-classed.

You are getting error from this Character class, which is being implicitly imported. Beware!.

edited Dec 14 '18 at 13:43

Andrei Suvorkov

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answered Dec 14 '18 at 12:36

Jabongg

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"Cannot subclass the final class" error, but the class is not final

4 Answers4