Should You Use == or equals() for Comparing Java Enum Members?

What is the best method for comparing two members of a Java enum: == or equals()?

public void useEnums(SomeEnum a) {
    if (a.equals(SomeEnum.SOME_ENUM_VALUE)) {
        ...
    }
}

public void useEnums2(SomeEnum a) {
    if (a == SomeEnum.SOME_ENUM_VALUE) {
        ...
    }
}

When comparing enum members in Java, you can safely use either the == operator or the equals() method. This is due to how Java enums are implemented, but each method has its implications and best practices that should be considered.

// Example of comparing enums using both approaches
if (a == SomeEnum.SOME_ENUM_VALUE) {
    // This works
}

if (a.equals(SomeEnum.SOME_ENUM_VALUE)) {
    // This also works
}

Causes

• Java enums are singleton instances, meaning each enum constant is a unique instance.
• Enums are compared based on their reference, not their values, making == a legitimate choice.

Solutions

• Use == for comparing enum constants for clarity and performance efficiency.
• Use equals() if you prefer to maintain consistency with other types of objects to avoid confusion.

Mistake: Using == when comparing objects of different types, which will cause a compile-time error.

Solution: Ensure both operands are of the same enum type when using ==.

Mistake: Confusing enum comparison with regular object comparison, leading to misuse of .equals() with null references.

Solution: Vector out potential null values by putting the constant on the left side: SomeEnum.SOME_ENUM_VALUE.equals(a)