public class SimpleSingleton {
    private static SimpleSingleton singleInstance =  new SimpleSingleton();

    private SimpleSingleton() {
    }

    public static SimpleSingleton getInstance() {

        return singleInstance;
    }
}

調用方法

public enum SimpleSingleton {
    INSTANCE;
    public void doSomething() {
    }
}

SimpleSingleton.INSTANCE.doSomething();
 

Java演示設計模式中的單件模式的代碼