How to Implement Enum Flags in Java Similar to C#?

How can I implement a similar functionality to C# Enum Flags Attribute in Java?

public enum FilePermissions {
    READ(1),
    WRITE(2),
    EXECUTE(4);

    private final int value;

    FilePermissions(int value) {
        this.value = value;
    }

    public int getValue() {
        return value;
    }

    public static int combine(FilePermissions... permissions) {
        int combined = 0;
        for (FilePermissions permission : permissions) {
            combined |= permission.getValue();
        }
        return combined;
    }

    public static boolean hasPermission(int combined, FilePermissions permission) {
        return (combined & permission.getValue()) == permission.getValue();
    }
}

In C#, the Enum Flags attribute allows enumerated types to represent a combination of options using bitwise operations. In Java, we don’t have a built-in Flags attribute, but we can achieve similar functionality by defining our enum with specific integer values that correspond to bit flags.

// Using the FilePermissions enum defined above
int myPermissions = FilePermissions.combine(FilePermissions.READ, FilePermissions.WRITE);

boolean canRead = FilePermissions.hasPermission(myPermissions, FilePermissions.READ); // true
boolean canExecute = FilePermissions.hasPermission(myPermissions, FilePermissions.EXECUTE); // false

Causes

• Understanding that Java's enums support a similar structure but lack the Flags attribute.
• Recognizing the need for bitwise operations to manage multiple enum values.

Solutions

• Define the enum with values that represent distinct bits using powers of two.
• Implement methods to combine the enum values using bitwise OR and to check for the presence of a specific flag using bitwise AND.

Mistake: Not initializing enum values as powers of two, which may cause overlapping bits.

Solution: Always use distinct powers of two (1, 2, 4, 8, etc.) for your enums.

Mistake: Failing to use the bitwise operators correctly when combining or checking permissions.

Solution: Ensure you understand how to properly use & and | operators for combining and checking flags.