Design Pattern Learning Notes (ix)-singleton mode

Source: Internet
Author: User
Tags static class

The book "Design Pattern" is described in the singleton mode:

Guarantees that a class has only one instance and provides a global access point to access it.

This model is relatively simple, here is an example:

public class Singleton {
 private static Singleton instance;
 private Singleton(){

 }
 public static Singleton getInstance(){
  if(instance==null)
  instance=new Singleton();
  return instance;
 }
}
This program is not a problem running in a single thread, but it can not run in a multi-threaded environment, if you want to run in a multi-threaded environment, you must modify the following:

public class Singleton {
 private static class Instance{
  static final Singleton instance=new Singleton();
 }
 private Singleton(){

 }
 public static Singleton getInstance(){
  return Instance.instance;
 }
}

This can be done because the static internal class instance will only be loaded once. The single State design mode running in multithreading is also called double-checked looking mode.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.