关于线程同步的几点学习体会

直接上代码


package com.nbgame.thread;

import java.util.HashMap;

public class HashMapDemo {

private static HashMap map = new HashMap();

/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub

}

/**
* 减少花费时间的办法之二，减少同步块的代码，减少了争用的时间
*
* @param userName
* @return
*/
public boolean userHasAdminAccess(String userName) {
String key = "users. " + userName + ".accessRights";
String rights;
synchronized (map) {
rights = (String) map.get(key);
}
return ((rights != null) && (rights.indexOf("ADMIN") >= 0));
}

private static HashMap userMap = new HashMap();
private static HashMap serviceMap = new HashMap();

/**
* 减少策略2： 采用2个同步线程来处理争用问题 它用两个单独的散列表来存储用户信息和服务信息，如清单 3 所示。
*
* @param user
* @param userInfo
*/
public synchronized void setUserInfo(String user, UserInfo userInfo) {
userMap.put(user, userInfo);
}

public synchronized UserInfo getUserInfo(String user, UserInfo userInfo) {
return (UserInfo) userMap.get(user);
}

public synchronized void setServiceInfo(String service,
ServiceInfo serviceInfo) {
serviceMap.put(service, serviceInfo);
}

public synchronized ServiceInfo getUserInfo(String service,
ServiceInfo serviceInfo) {
return (ServiceInfo) serviceMap.get(service);
}

/**
* 减少策略3： 它用两个单独的散列表来存储用户信息和服务信息， 并且减少争用的粒度。
*
* @param user
* @param userInfo
*/
public void setUserInfo1(String user, UserInfo userInfo) {
synchronized (userMap) {
userMap.put(user, userInfo);
}
}

public UserInfo getUserInfo1(String user, UserInfo userInfo) {
synchronized (userMap) {
return (UserInfo) userMap.get(user);
}
}

public void setServiceInfo1(String service, ServiceInfo serviceInfo) {
synchronized (serviceMap) {
serviceMap.put(service, serviceInfo);
}
}

public ServiceInfo getUserInfo1(String service, ServiceInfo serviceInfo) {
synchronized (serviceInfo) {
return (ServiceInfo) serviceMap.get(service);
}
}
}

class UserInfo {
private String name;
private int id;

}

class ServiceInfo {
private String name;
private int id;
}