单例模式

简介

确保整个服务一个对象只被初始化一次

 

懒汉模式：调用方法时候才初始化

public class LazyMode {

    private LazyMode() {

    }

    private static volatile LazyMode hungryMode;

    public static LazyMode getInstance() {
        if (hungryMode == null) {
            synchronized (LazyMode.class) {
                if (hungryMode == null) {
                    hungryMode = new LazyMode();
                }
            }
        }
        return hungryMode;
    }
}

 

 

饿汉模式：容器初始化时候就已经初始化

public class HungerMode {

    private HungerMode() {
    }

    private static final HungerMode fullMode = new HungerMode();

    public static HungerMode getInstance() {
        return fullMode;
    }
}

 

 

枚举实现单例

 

public enum EnumMode {
    SINGLE;
    private ThreadPoolExecutor threadPoolExecutor;

    EnumMode() {
        threadPoolExecutor = new ThreadPoolExecutor(5, 5, 100, TimeUnit.SECONDS, new LinkedBlockingDeque());
    }

    public void startTask(Runnable runnable) {
        threadPoolExecutor.execute(runnable);
    }
}