單例模式

1.普通單例模式

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

2.線程安全的單例模式

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