Enum Comparison Best Practices in Java with 4 Reasons
In Java, enums are a special type of class that represents a group of constants. Enum constants are treated as objects, which means that you can use them to call methods, store them in variables, and so on. When it comes to comparing enum constants, you have two options: using the “==” operator or the “equals” method to check the equality of the enums. Here are a few reasons why using the “==” operator is generally considered to be a better approach to check the enums:
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- Performance: Using the “==” operator is generally faster than using the “equals” method to compare enums in Java because it does not involve any method calls or object allocation. The “==” operator simply checks if two references point to the same object in memory, which is a quick and easy operation. On the other hand, the “equals” method compares the values of the objects, which can be more expensive. But this is the case for a single comparison. If there are repeating enum comparison operations, performance can be the same or even equals method can out perform.
public class Performance {
enum Color {
RED, GREEN, BLUE
}
public static void main(String[] args) {
long startTime, endTime;
Color c1 = Color.RED;
Color c2 = Color.RED;
// Single comparing enums using ==
startTime = System.nanoTime();
if (c1 == c2) {
// do something
}
endTime = System.nanoTime();
System.out.println("Single comparing enums using == took " + (endTime - startTime) + " ns");
// Single comparing enums using equals
startTime = System.nanoTime();
if (c1.equals(c2)) {
// do something
}
endTime = System.nanoTime();
System.out.println("Single comparing enums using equals took " + (endTime - startTime) + " ns");
// Comparing enums using ==
startTime = System.nanoTime();
for (int i = 0; i < 1000000; i++) {
if (c1 == c2) {
// do something
}
}
endTime = System.nanoTime();
System.out.println("Multiple comparing enums using == took " + (endTime - startTime) + " ns");
// Comparing enums using equals
startTime = System.nanoTime();
for (int i = 0; i < 1000000; i++) {
if (c1.equals(c2)) {
// do something
}
}
endTime = System.nanoTime();
System.out.println("Multiple comparing enums using equals took " + (endTime - startTime) + " ns");
}
}Here the output of the above
Single comparing enums using == took 333 ns Single comparing enums using equals took 3958 ns Multiple comparing enums using == took 5984917 ns Multiple comparing enums using equals took 5970167 ns
- Null safety: When comparing enums using the “==” operator, you don’t have to worry about null values. If either of the operands is null, the “==” operator will return false, which is a safe and expected behavior. On the other hand, if you try to compare enums using the “equals” method and one of the operands is null, you will get a NullPointerException at runtime. To avoid this, you need to explicitly check for null values before calling the “equals” method.
public class NullSafety {
enum Color {
RED, GREEN, BLUE;
}
public static void main(String[] args) {
CompileTimeSafety.Color c1 = null;
CompileTimeSafety.Color c2 = CompileTimeSafety.Color.GREEN;
System.out.println(c1 == c2); // This will print "false"
System.out.println(c1.equals(c2)); // This will throw exception
}
}false Exception in thread “main” java.lang.NullPointerException
- Compile-time vs. runtime checks: When you use the “==” operator to compare enums, the check is performed at compile time, which means that any mistakes or typos in your code will be caught early on. On the other hand, when you use the “equals” method to check the equality of enums, the check is performed at runtime, which means that errors may not be caught until your code is actually executed. This can lead to more difficult and time-consuming debugging. If we try to compare two enums with the equals method, it will always return a value either true or false.
When we try to compare a Color enum that is defined in a class other than the Performance class with the color value of an object that uses the Color enum from the Performance class that we have defined in the previous bullet point, equals method accepts the provided value to compare and it always returns false. But “==” operator causes compile time error.
public class BlueObject {
private Performance.Color color;
public BlueObject() {
this.color = Performance.Color.BLUE;
}
public Performance.Color getColor() {
return color;
}
}public class CompileTimeSafety {
enum Color {
RED, GREEN, BLUE;
}
public static void main(String[] args) {
BlueObject objectToCheck = new BlueObject();
Color c1 = Color.BLUE;
System.out.println(c1.equals(objectToCheck.getColor())); // This will print "false"
System.out.println(c1 == objectToCheck.getColor()); // This will not compile
}
}- Readability: When comparing enums using the “==” operator, the code is more readable and concise than when using the “equals” method. This is because the “==” operator is a well-known comparison operator in Java, and its use in enum comparisons is more intuitive and straightforward.
public class Readability {
enum Day {
MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY
}
public static void main(String[] args) {
Day today = Day.MONDAY;
// Comparing enums using ==
if (today == Day.MONDAY) {
System.out.println("Today is Monday");
}
// Comparing enums using equals
if (today.equals(Day.MONDAY)) {
System.out.println("Today is Monday");
}
}
}In conclusion, when comparing enums in Java, using the “==” operator is generally preferred over the “equals” method because it provides better performance and null safety. Additionally, enums provide type safety, which ensures that only valid values can be used, making code more reliable and easier to maintain. Finally, while the readability difference between the two approaches may be minimal, using the “==” operator is considered more concise and intuitive, leading to more readable code.
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