() {12.returninstance; 13. } 14.}This type of writing does not occur concurrency problems, but it is a hungry man-style, after ClassLoader loaded class Kerrigan instance will be created the first time, a hungry man style of creation in some scenarios will not be used: for example, the creation of the instance is dependent on parameters or configuration files, You must call a method before getinstance () to set the parameter to it, so that the single
(multiple case mode)5, more flexible than class operation Four, the single case pattern applies the scene 1. When a class can have only one instance and the customer can access it from a well-known access point2, when this unique instance should be extensible through subclasses. And the user should be able to use an extended instance without changing the code.V.
minimize the scope of the synchronization code, do not directly in the Sevice method and response methods to use synchronization, which can seriously affect performance.2, property of the thread-safe: Servletcontext,httpsession,servletrequest object in the properties.ServletContext: (thread is not secure)ServletContext is a multithreaded simultaneous read/write attribute, threads are unsafe. You want to synchronize the read and write properties or Deep Clone (). Therefore, in the context of the
in other ways to share in multiple servlets, for example, we can use a singleton mode to process the shared data.HttpSession: (thread is not secure)The HttpSession object exists during a user session and can only be accessed in a thread that processes requests that belong to the same session, so the session object's property access is theoretically thread-safe.When a u
used in other ways to share in multiple servlets, for example, we can use a singleton mode to process the shared data.HttpSession: (thread is not secure)The HttpSession object exists during a user session and can only be accessed in a thread that processes requests that belong to the same session, so the session object's property access is theoretically thread-safe.When a
single case (Singleton) mode is also called a single state mode
Overview: the Singleton (Singleton) pattern requires that a class has and has only one instance, and provides a global access point. This raises the question of how to bypass conventional constructors and provide a mechanism to ensure that a class has onl
In the previous fifth (a), a socket example is a single-threaded, that is, the server can only accept a connection from a client side, in order to better illustrate the socket single-threaded and blocking mode, the following example is modified.1. Single thread + blocking + InteractiveThe previous example is
The singleton pattern in this paper is divided into strict single case mode and not strict single case mode. The singleton pattern requires that a class have an instance that has a public interface that can access the instance. Strict singleton mode requires only one instanc
Single case mode, which can be said to be the simplest of the 23 design patterns of GOF.
This pattern is relatively independent of several other modes, it is only responsible for controlling its own instantiation quantity single (instead of considering what kind of instance produces for the user), it is very interesti
Single case Mode singletonWord 827 Read 224 Comments 0 likes This is my study of "Android source design mode analysis and combat" in the process of a single-case mode to make a record. Convenient to look at anytime later.Singleton mode
, then use a single example mode can be very convenient to implement. This can be frontcontroller part of ZF.
3, in a page request, easy to debug, because all the code (such as database Operation class DB) are concentrated in a class, we can set hooks in the class, output log, so as to avoid everywhere var_dump, Echo
Single Case class
1. Constructors need to b
the __init__ method of the Foo class (the object of type), which is used to initialize the object. obj = Foo () # 2nd Step: __call__ method for executing food obj () "" "Singleton Mode Example:ImportThreadingclassSingletontype (type): _instance_lock=Threading. Lock ()def __call__(CLS, *args, * *Kwargs):if notHasattr (CLS,"_instance"): With Singletontype._instance_lock:if notHasattr (CLS,"_instance"): Cls._instance= Super (SINGLETONTYPE,CLS).__call_
Application ScenariosBecause singleton mode generates only one instance, it reduces system performance overhead (e.g., when an object is generated that requires more resources, such as reading a configuration and generating other dependent objects, it can be resolved by producing a singleton object directly at application startup and then permanently residing in memory)
Task Manager in Windows;
File system, an operating system can only ha
pros and cons of lazy mode and a hungry man mode:Lazy mode, which is characterized by the slow speed at which objects are obtained at runtime, but faster when loading classes. It consumes resources only a fraction of the time throughout the application's life cycle.A hungry man mode, which is characterized by the slow loading of the class, but the speed at which
corresponding class. The beanfactory itself only needs an instance, so using singleton mode, here is a single example of registration:Package Com.example.factorymode.util;import Java.io.ioexception;import Java.util.hashmap;import java.util.Map; Import Java.util.properties;import Com.example.factorymode.bean.user;import Com.example.factorymode.engine.iuserengine;public class Beanfactory {private static Prop
to the server.
For example, if the remote user computer system is installed in c: \ WINNT, you can choose Start> RUN> enter c: \ winnt \ system32 \ In the taskbar \Mstsc.exe/console"To achieve the above-mentioned function of not enabling new end users to log on to the remote server.
TIPS:1. the Windows XP Remote Terminal Service is a single user, that is to say,
Original: http://www.cocoachina.com/industry/20130510/6168.htmlhttp://www.justinyan.me/post/1306single-case modeThere are also many classes in the IOS SDK that use singleton mode, for example,uiapplication: When the program starts, it calls the Uiapplicationmain method, in which a UIApplication object is instantiated, Subsequent calls to the Sharedapplication method anywhere in the program will return a uiapplication instance associated with the curre
= new Singletonclass ();
}
}
return instance;
}
Private Singletonclass () {
}
}First, remove the synchronization of getinstance () and then load the sync lock on the IF statement. But such modifications do not work: because the getinstance () is necessarily synchronized every time it is invoked, there is a performance problem. If...... What if we were to determine if we were going to sync for null?
public class Singletonclass {
private static singletonclass ins
think it makes sense to just have multiple scenarios for a single page-level request and need to share the same object resource.2, the single case mode in PHP application occasions:(1) Application and database interactionA large number of database operations exist in an application, such as a database handle to connect to a database, and a singleton pattern avoi
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