양피서 APP(Android Edition) 개발 시리즈(22) 10분 초 이해 단일 모드

단일 모드 정의:

단일 모드의 이점:

아사자식:

public class Singleton1 {
    // 
    private Singleton() {}
    //  
    private static final Singleton single = new Singleton();
    //  
    public static Singleton getInstance() {
        return single;
    }
}

게으름뱅이식(一):

public class Singleton {  
    private static Singleton instance;  
    private Singleton (){}  
  
    public static Singleton getInstance() {  
    if (instance == null) {  
        instance = new Singleton();  
    }  
    return instance;  
    }  
}

게으름뱅이식(二):

public class Singleton {  
    private static Singleton instance;  
    private Singleton (){}  
    public static synchronized Singleton getInstance() {  
    if (instance == null) {  
        instance = new Singleton();  
    }  
    return instance;  
    }  
} 

정적 내부 클래스:

public class Singleton {  
    private static class SingletonHolder {  
        private static final Singleton INSTANCE = new Singleton();  
    }  
    private Singleton (){}  
    public static final Singleton getInstance() {  
        return SingletonHolder.INSTANCE; 
    }  
}

이중 잠금 확인:

public class Singleton {
    private volatile static Singleton singleton;

    private Singleton() {
    }

    public static Singleton getSingleton() {
        if (singleton == null) {
            synchronized (Singleton.class) {
                if (singleton == null) {
                    singleton = new Singleton();
                }
            }
        }
        return singleton;
    }
} 

요약: