Java synchronized memo

1   Public   Class Test {
 2  
 3   Public   Void Method0 (){ //  ...}  //  Common functions  
  4  
 5   Public   Synchronized  Void Method1 (){ //  ...}  //  Synchronous Functions  
  6  
 7   Public   Void Method2 (){
 8  Synchronized ( This ){ //  ...} //  Synchronization with the current object as the lockCodeBlock  
  9 }
 10  
 11   Public   Void Method3 (someobject so ){
 12  Synchronized (So ){ //  ...}  //  Synchronization code block with an object as the lock 
  13 }
 14  
 15   Public   Void Method4 (){
 16  //  ...  
  17  Private   Byte [] Lock = New   Byte [0]; //  Special instance variables  
  18  Synchronized (Lock ){ //  ...}  //  Synchronous Code Block
  19  //  ...  
  20 }
 21  
22   Public   Synchronized   Static   Void Method5 (){...} //  Static synchronization Functions  
  23  
 24   Public   Void Method6 (){
 25       Synchronized (Test. Class ){...}//  Class literal is used as the synchronization lock code block.  
  26 }
 27  
 28 }

1. synchronous block synchronized (this) {...} In Method1 and method2 ){...} the obtained synchronization locks are instance objects like test, that is, Object locks, so Method1 and method2 are equivalent.

2. When multiple concurrent threads access"Same"When the synchronization function or synchronization block in the object is obtained, the thread that acquires the object lock is executed. During the execution of this thread, other threads that want to access the object's synchronization function or synchronization block (whether or not the same synchronization function or synchronization block) will be blocked until the object lock is obtained, of course, the non-synchronous method to access the object or the thread of the synchronization block are not restricted by the object lock and can be accessed directly.

Iii. synchronized (this ){...} this indicates the object that calls this method. If the two threads call t1 and t2 (class test instantiation) respectively, the synchronization block is invalid for the two threads. You can use the synchronization block synchronized (SO) {...} In method3 ){...} method.

4. What if I want to synchronize some code in the function? In method4, a special instance variable acts as a lock.

5. Synchronized synchronized (test. class ){...} the obtained synchronization lock is a class lock, that is, the class test lock, rather than the class test object lock.

6. Because the class lock is different from the object lock, Method1 and method5 do not constitute synchronization in the multi-thread concurrent environment.