Compare enums with == instead of equals() in Java

2017-11-22
JAVA

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TIL you should compare enums with == instead of equals() in Java.

a == SomeEnum.ENUM_VALUE
/* instead of */
a.equals(SomeEnum.ENUM_VALUE)

Last week I saw this pull request in a repository on GitHub. This PR triggered me to take a look at how I should compare enums in Java.

I used to compare enums with equals(). In the API I saw that equals() on an enum is the same as ==, because this is what the equals() implementation looks like:

public final boolean equals(Object other) {
    return this==other;
}

I found two good points why you should use == instead of equals() when comparing enums.

Prevent NullPointerExceptions

If you use == to compare an enum with NULL, it will return false. However, if you use equals() to compare an enum with NULL, you will probably get a NPE.

Type safety

The == operator checks if both enum objects are from the same enum type or not at compile time. This is in contrast to equals(), which will return false at runtime. I prefer—and I think you should too—to detect errors at compile time.