Java Enums: Should You Use == or equals() to Compare Members?

Comparing Java Enum Members: == vs. equals()

When working with Java's enum types, developers often face the question of whether to use the equality operator (==) or the equals() method to compare enum members. This question arises because enums are compiled into classes, leading to confusion about the underlying implementations.

Understanding Java Enums

Java enums are classes with private constructors and public static members representing the enum values. These members are essentially constants and cannot be altered.

Comparing Enum Members

Both the == operator and the equals() method can be used to compare enum members. The equals() method provides a standard way to compare objects in Java, while == compares the references of the objects being compared.

Technical Equivalence

Inspecting the source code of the equals() method reveals that it simply defers to the == operator. This means that, technically, both approaches are equivalent for comparing enum members.

Recommended Approach

However, it is generally recommended to use the == operator for comparing enum members. This approach is:

• Null-Safe: The == operator returns false when comparing an enum member to null, whereas equals() might throw a NullPointerException.

Example

The following code demonstrates the use of both == and equals() to compare enum members:

public enum MyEnum {
    A, B, C
}

public static void main(String[] args) {
    MyEnum a = MyEnum.A;
    MyEnum b = MyEnum.B;

    System.out.println(a == b); // false
    System.out.println(a.equals(b)); // false
}

In this example, both == and equals() return false because a and b refer to different enum members.

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