public class SychronizdDemo {

The static Integer count=0; 
Public static void incr () {
Synchronized (count) {
Try {
Thread.sleep (1); 
{} catch InterruptedException (e) 
e.printStackTrace(); 
} 
count++; 
} 
} 
Public static void main (String [] args) throws IOException, InterruptedException {
for(int i=0; i<1000; I++) {
New Thread (() - & gt; SychronizdDemo. Incr ()). The start (); 
} 
Thread.sleep (5000); 
System. The out. Println (" result: "+ count); 
} 
} 

Why sleep not releases the lock and the output result is less than 1000 number???????

CodePudding user response:

Personally think that an Integer from 0-127 with Java memory address of the default, so every time after update the count, in fact, the monitor has changed not guarantee must be thread safe

CodePudding user response:

Said some of the issues that should be after every + +, the count is no longer the same count, he will return again new integer, so the monitor has been changed,
Is the scope of and integer cache - 128-127

CodePudding user response:

Sleep itself will not release the lock, after count++ count object has changed, so use class object lock is ok,

CodePudding user response:

Upstairs, positive solutions [align=center]
Lock the object has changed, you always change the Integer,

Program to which is a step in the right, which get a lock object as a lock) :

 
Public class SychronizdDemo {
The static Object lock=new Object (); 
The static Integer count=0; 
Public static void incr () {
Synchronized (lock) {
Try {
Thread.sleep (1); 
{} catch InterruptedException (e) 
e.printStackTrace(); 
} 
count++; 
System. The out. Println (count); 
} 
} 
Public static void main (String [] args) throws IOException, InterruptedException {
for(int i=0; i<1000; I++) {
New Thread (() - & gt; SychronizdDemo. Incr ()). The start (); 
} 
Thread.sleep (5000); 
System. The out. Println (" result: "+ count); 
} 
} 

Can look at my blog: https://blog.csdn.net/Kurry4ever_/article/details/109557532