Pattern: Singleton Mode and Its serialization implementation

The Singleton mode can be written in many ways. A good article is recommended.

Http://devbean.blog.51cto.com/448512/203501

After reading the above article, you can take a look at my Singleton implementation from objective Java.

1. Simplest Singleton mode implementation

//Singleton with final field - page 10public class Elvis {public static final Elvis INSTANCE = new Elvis();private Elvis() {// ...}// ... // Remainder omittedpublic static void main(String[] args) {System.out.println(Elvis.INSTANCE);}}

2. Implement the singleton mode using the static factory Method

//Singleton with static factorypublic class Elvis {private static final Elvis INSTANCE = new Elvis();private Elvis() {// ...}public static Elvis getInstance() {return INSTANCE;}// ... // Remainder omittedpublic static void main(String[] args) {System.out.println(Elvis.INSTANCE);}}

The implementation differences between the two methods are explained below

3. Implement Singleton mode for static internal classes

/** * When the getInstance method is invoked for the first time, it reads * SingletonHolder.uniqueInstance for the first time, causing the * SingletonHolder class to get initialized.The beauty of this idiom is that the * getInstance method is not synchronized and performs only a field access, so * lazy initialization adds practically nothing to the cost of access. A moder * VM will synchronize field access only to initialize the class.Once the class * is initialized, the VM will patch the code so that subsequent access to the * field does not involve any testing or synchronization. *  * @author mark *  */public class Singleton {// an inner class holder the uniqueInstance.private static class SingletonHolder {static final Singleton uniqueInstance = new Singleton();}private Singleton() {// Exists only to default instantiation.}public static Singleton getInstance() {return SingletonHolder.uniqueInstance;}// Other methods...}

For the third implementation benefit, please refer to the English note above. I would like to learn from the master!

4. Singleton mode serialization

/ Serialzable Singleton - Page 11import java.io.*;public class Elvis {    public static final Elvis INSTANCE = new Elvis();    private Elvis() {        // ...    }    // ...  // Remainder omitted    // readResolve method to preserve singleton property    private Object readResolve() throws ObjectStreamException {        /*         * Return the one true Elvis and let the garbage collector         * take care of the Elvis impersonator.         */        return INSTANCE;    }    public static void main(String[] args) {        System.out.println(Elvis.INSTANCE);    }}

You can continue to read this book for more explanations.