@UtilityClass

Since

@UtilityClass was introduced as an experimental feature in lombok v1.16.2.

Experimental

Experimental because:

  • Some debate as to whether its common enough to count as boilerplate.
Current status: positive - Currently we feel this feature may move out of experimental status with no or minor changes soon.

Overview

A utility class is a class that is just a namespace for functions. No instances of it can exist, and all its members are static. For example, java.lang.Math and java.util.Collections are well known utility classes. This annotation automatically turns the annotated class into one.

A utility class cannot be instantiated. By marking your class with @UtilityClass, lombok will automatically generate a private constructor that throws an exception, flags as error any explicit constructors you add, and marks the class final. If the class is an inner class, the class is also marked static.

All members of a utility class are automatically marked as static. Even fields and inner classes.

With Lombok

01 import lombok.experimental.UtilityClass;
02 
03 @UtilityClass
04 public class UtilityClassExample {
05   private final int CONSTANT = 5;
06 
07   public void addSomething(int in) {
08     return in + CONSTANT;
09   }
10 }

Vanilla Java

01 public final class UtilityClassExample {
02   private static final int CONSTANT = 5;
03 
04   private UtilityClassExample() {
05     throw new java.lang.UnsupportedOperationException("This is a utility class and cannot be instantiated");
06   }
07 
08   public static void addSomething(int in) {
09     return in + CONSTANT;
10   }
11 }

Small print

There isn't currently any way to create non-static members, or to define your own constructor. If you want to instantiate the utility class, even only as an internal implementation detail, @UtilityClass cannot be used.