Design Pattern - Singleton

良葛格已分享許多方法與範例, 在此提供 Inner Class 的方法

public class SingletonDemo {

    private SingletonDemo() {
        // do something...
    }

    public static SingletonDemo getInstance() {
        return SingletonHolder.instance;
    }

    private static class SingletonHolder {
        private static final SingletonDemo instance = new SingletonDemo();
    }

    public void function1()....
    public void function2()....
}