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Java中的volatile和synchronized之间的区别(Difference between volatile and synchronized in Java)

 我想知道将变量声明为volatile并且始终访问Java（特别是J2ME）中的synchronized(this)块中的变量的区别？  
 根据这篇文章http://www.javamex.com/tutorials/synchronization_volatile.shtml有很多话要说，有很多差异，但也有一些相似之处。  
 我对这条信息特别感兴趣  
 
  ...  
  
   访问一个易失性变量从来没有阻止的可能性：我们只是做一个简单的读或写，所以不同于一个同步块，我们永远不会坚持任何锁;  
   因为访问volatile变量永远不会保持锁定，所以不适合我们想要读取更新写入作为原子操作的情况（除非我们准备“错过更新”）;  
  
 
 read-update-write是什么意思？ 不写也是更新还是他们只是意味着更新是写取决于读取的信息？  
 最重要的是，什么时候更适合声明变量，而不是通过synchronized访问变量？ 对依赖于输入的变量使用volatile是个好主意？ 例如，有一个名为render的变量通过渲染循环读取并由一个按键事件设置？ 

I am wondering at the difference between declaring a variable as volatile and always accessing the variable in a synchronized(this) block in Java? 
According to this article http://www.javamex.com/tutorials/synchronization_volatile.shtml there is a lot to be said and there are many differences but also some similarities. 
I am particularly interested in this piece of info: 
 
 ... 
  
  access to a volatile variable never has the potential to block: we're only ever doing a simple read or write, so unlike a synchronized block we will never hold on to any lock; 
  because accessing a volatile variable never holds a lock, it is not suitable for cases where we want to read-update-write as an atomic operation (unless we're prepared to "miss an update"); 
  
 
What do they mean by read-update-write? Isn't a write also an update or do they simply mean that the update is a write that depends on the read? 
Most of all, when is it more suitable to declare variables volatile rather than access them through a synchronized block? Is it a good idea to use volatile for variables that depend on input? For instance, there is a variable called render that is read through the rendering loop and set by a keypress event?

原文：https://stackoverflow.com/questions/3519664

更新时间：2023-09-20 10:09

最满意答案

 问题在于使用'错误'语法来创建服务 
 而不是使用：  
messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService'], 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
);
 
 我不得不使用：  
messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService', 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
]);
 
 我很快就用参数关闭了数组，由于我还在学习，我没有直接看到它，无论如何，我希望我可以帮助那些绊倒的人。 

The problem was in using the 'wrong' syntax to create the service 
 instead of using: 
messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService'], 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
);
 
I had to use: 
messageServices.factory('MessageService', 
    ['MessageData','localStorageService', 'UserService', 
    function(MessageData, localStorageService, UserService){
        return new MessageService(MessageData, localStorageService, UserService);
    }
]);
 
I closed the array with parameters to soon, and since I'm still learning I didn't see it directly, anyhow I hope I can help others who stumble upon this.

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Java中的volatile和synchronized之间的区别(Difference between volatile and synchronized in Java)

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