What does @Override mean in this java code?

Question

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When do you use Java's @Override annotation and why?
Java, What does @Override mean?

I was checking out Drools Planner example source code and I came across code like this:

@Override
protected Solver createSolver() {
    XmlSolverConfigurer configurer = new XmlSolverConfigurer();
    configurer.configure(SOLVER_CONFIG);
    return configurer.buildSolver();
}

protected Solver createSolverByApi() {
    // Not recommended! It is highly recommended to use XmlSolverConfigurer with an XML configuration instead.
    SolverConfig solverConfig = new SolverConfig();

    solverConfig.setSolutionClass(NQueens.class);
    .....TRUNCATED....
    solverPhaseConfigList.add(localSearchSolverPhaseConfig);
    solverConfig.setSolverPhaseConfigList(solverPhaseConfigList);
    return solverConfig.buildSolver();
}

As far as I understand createSolver() and createSolverByApi() are supposed to return Solver objects when you explicitly call them.

What does the @Override mean here? What is the general meaning of the @ term?

EDIT: My very bad; I inadvertently duplicated What does @Override mean?

At least make *some* attempt at reading the documentation... http://docs.oracle.com/javase/6/docs/api/java/lang/Override.html — skaffman, Jan 16 '12 at 07:35

Buhake Sindi · Accepted Answer · 2012-01-16T07:41:18.103

17

The @ is Java Annotations.

The @Override means that the method is overriding the parent class (in this case createSolver).

The Javadoc states for @Override:

Indicates that a method declaration is intended to override a method declaration in a superclass.

This annotation is useful for compile-time checking to verify that the method you're overriding is valid (overridden correctly).

edited Jan 16 '12 at 07:41

answered Jan 16 '12 at 07:35

Buhake Sindi

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So, can a method be overridden at all without this? What happens if this is excluded when a method is intended to overwrite another? – Aaron Franke Nov 04 '16 at 04:00
2

It can be overridden without the annotation. It just helps developers know that there is a parent class method that has been overridden by a child class. – Buhake Sindi Nov 04 '16 at 09:06

score 3 · Answer 2 · edited Jun 14 '16 at 17:37

3

See the Java tutorial about annotations, and there the 'Annotations used by the compiler' section. A quick copy-paste from the relevant part

@Override—the @Override annotation informs the compiler that the element is meant to override an element declared in a superclass (overriding methods will be discussed in the the lesson titled "Interfaces and Inheritance").

edited Jun 14 '16 at 17:37

TheSynnott

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answered Jan 16 '12 at 07:36

Robin

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score 2 · Answer 3 · edited Oct 12 '13 at 04:29

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This is called an Annotation. It is actually not compiled into special code, but it helps avoiding errors: essentially, it indicates that the method overrides a method of a superclass. Not having this annotation can cause warnings, having this annotation but no superclass that has a method with the same annotation is even an error.

This avoids refactoring errors: if the method in the superclass is renamed, and the override not, then it will become an error.

edited Oct 12 '13 at 04:29

SpringLearner

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answered Jan 16 '12 at 07:35

Has QUIT--Anony-Mousse

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No special meaning to the compiler ... how can it generate a compile error if the compiler does not assign a special meaning to it. See my answer. It is discussed in the 'Annotations used by the compiler' section, so it certainly has special meaning to the compiler – Robin Jan 16 '12 at 07:38
As in: no run time retention AFAIK. – Has QUIT--Anony-Mousse Jan 16 '12 at 07:54
@Anony-Mousse good explanation so +1 also I have edited your answer for correct spelling – SpringLearner Oct 12 '13 at 04:30

score 0 · Answer 4 · answered Jan 16 '12 at 07:38

This is java annotation , in your case you would use @Override above a method to be sure that you are overriding a super class method , if you use it and the method is not in the super class because you type it name wrong for example an error will occur at compile time .

score 0 · Answer 5 · answered Jan 16 '12 at 07:40

0

I want to add this : declared in a superClass or method declared in an interface (since Java 6)

answered Jan 16 '12 at 07:40

Benoit

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No, annotation got introduced since Java 5. `@Override` got introduced since Java 5 (by Joshua Bloch). – Buhake Sindi Jan 16 '12 at 07:44
declared in a superClass since java 5 and declared in interface since java6 – Benoit Jan 17 '12 at 11:07

What does @Override mean in this java code?

5 Answers5