lombok
Annotation Type Singleton

@Target(value=TYPE)
@Retention(value=SOURCE)
public @interface Singleton

Two popular singleton templates.

Since not much code is generated, the annotation also acts as documentation.

With lombok:

 @Singleton
 class MySingleton {
        public MySingleton() {
        }
 }
 

 enum MySingleton {
        INSTANCE;
        MySingleton() {
        }
 
        public static MySingleton getInstance() {
                return INSTANCE;
        }
 }
 

Note: If you don't like the enum approach, try the holder approach using
@Singleton(style = Singleton.Style.HOLDER).

style

public abstract Singleton.Style style

Specifies the singleton-style to use, default is ENUM.

Default:

lombok.Singleton.Style.ENUM