public class Singleton{
	private static Singleton uniqueInstance; // 利用一個(gè)靜態(tài)變量來記錄Singleton類的唯一實(shí)例
	private Singleton(){} // 把構(gòu)造器聲明為私有的，只有自Singleton類內(nèi)才可以調(diào)用構(gòu)造器
	// 用getInstance()方法實(shí)例化對(duì)象，并返回這個(gè)實(shí)例
	public static Singleton getInstance(){
		if (uniqueInstance == null){
			uniqueInstance = new Singleton();
		}
		return uniqueInstance;
	}
}

public  class Singleton{
	private static Singleton uniqueInstance;

	private Singleton(){}

	public static synchronized Singleton getInstance(){
		if(uniqueInstance == null){
			uniqueInstance = new Singleton();
		}
		return uniqueInstance;
	}
}

public class Singleton{
	// 在靜態(tài)初始化器（static initializai）中創(chuàng)建單件。這樣可以保證線程安全（thread sate）
	private static Singleton uniqueInstance = new Singleton();

	private static Singleton getInstance(){
		return uniqueInstance;
	}
	
}

public class Singlenton{
	// volatile關(guān)鍵詞：當(dāng)uniqueInstance變量被初始化成Singleton實(shí)例時(shí)，多個(gè)線程正確地處理uniqueInstance變量
	private volatile static Singleton uniqueInstance();
	
	private Singleton(){}

	public static Singleton getInstance(){
		// 檢查實(shí)例，如果不存在，就進(jìn)入同步區(qū)塊
		if(uniqueInstance == null){
			// 進(jìn)入?yún)^(qū)塊后，再檢查一次。如果仍是null，才創(chuàng)建實(shí)例
			synchronized (Singleton.class){
				if(uniqueInstance == null){
					uniqueInstance = new Singleton();
				}
			}
		}
		return uniqueInstance;
	}
}

class Singleton:
	def getSingleton:
		pass
singleton = Singleton()

class Singleton(object):
    _instance = None
    def __new__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = object.__new__(cls, *args, **kwargs)
        return cls._instance
    def __init__(self):
        pass

def singleton(cls):
	# 創(chuàng)建一個(gè)私有變量，類型為字典，用來存放類地址的
    _instance = {}

    def inner():
    	# 如果類不存在
        if cls not in _instance:
        	# 實(shí)例化一個(gè)類并存放在字典里
            _instance[cls] = cls()
        return _instance[cls]
    return inner
    
@singleton
class ClassName(object):
    def __init__(self):
        pass

class Singleton(object):
    def __init__(self, cls):
        self._cls = cls # 接受類名
        self._instance = {} # 存放類地址
    def __call__(self):
        if self._cls not in self._instance:
        	# 實(shí)例化類并存放在字典內(nèi)
            self._instance[self._cls] = self._cls()
        return self._instance[self._cls]

@Singleton
class ClassName(object):
    def __init__(self):
        pass