Java synchronization Mechanism object lock usage Comparison

Class Sync {private byte[] lock = new Byte[0];        public void Sync () throws Interruptedexception {synchronized (lock) {runthread ();        }} public void Thissync () throws Interruptedexception {synchronized (this) {runthread ();     }} public synchronized static void Staticsync () throws Interruptedexception {//synchronous static function Runthread (); } public void Classsync () throws Interruptedexception {//synchronized (Sync.class) {Runthread (        );        }} private static void Runthread () throws Interruptedexception {Thread current = Thread.CurrentThread ();        System.out.println ("Current thread ID:" + current.getid () + "Enter ...");        System.out.println ("1111");        Thread.Sleep (1000);        System.out.println ("2222");        Thread.Sleep (1000);        System.out.println ("3333");        Thread.Sleep (1000);        System.out.println ("4444");        Thread.Sleep (1000); System.Out.println ("5555");    System.out.println ("Current thread ID:" + current.getid () + "out ..."); }}

1. Whether the same thread lock object locks are reusable (that is, do not wait)

CONCLUSION: REUSABLE

public class Testobjectsynclock {    private static byte[] lock = new byte[0];//0 Length byte array object will be created more economically than any object. View compiled bytecode: Generate 0-length byte[] objects with only 3 opcode, and object lock = new Object () requires 7 lines of opcode. Public     static void Main (string[] args) throws Interruptedexception {    //1. The same thread lock object locks are reusable (that is, do not wait)----REUSABLE                synchronized (lock) {            new Thread (new Runnable () {public                void run () {                    try {                        thread.sleep ()};                    } catch (Interruptedexception e) {                        e.printstacktrace ();                    }                    System.out.println ("AAA");                }            ). Start ();            Lock.notify ();        }        Synchronized (lock) {            System.out.println ("BBB");            Lock.wait ();}}}   

Results:

Bbb
Aaa

2. Same object, multi-threaded access (one main thread, one new thread)

Conclusion: The lock is effective

  Thread current = Thread.CurrentThread ();         System.out.println ("Current thread ID:" +current.getid () + "start ...");       Final sync Sync =new sync ();               New Thread (New Runnable () {public                        void run () {                Thread current = Thread.CurrentThread ();                  System.out.println ("Current thread ID:" +current.getid () + "start ...");                try {                    sync.sync ();                } catch (Interruptedexception e) {                    e.printstacktrace ();}}}        ). Start ();                Sync.sync ();

Results:

Current thread Id:1start ...
Current thread Id:1enter ...
1111
Current thread Id:9start ...
2222
3333
4444
5555
Current thread id:1out ...
Current thread Id:9enter ...
1111
2222
3333
4444
5555
Current thread id:9out ...

3. Different objects, multi-threaded access

Conclusion: Lock is invalid

Thread current = Thread.CurrentThread ();        System.out.println ("Currret thread ID:" + current.getid () + "start ...");        Final Sync sync = new sync ();        Final Sync sync2 = new sync ();        New Thread (New Runnable () {public            void run () {                Thread current = Thread.CurrentThread ();                System.out.println ("Currret thread ID:" + current.getid () + "start ...");                try {                    sync2.sync ();                } catch (Interruptedexception e) {                    e.printstacktrace ();}}}        ). Start ();        Sync.sync ();

Results:

Currret Thread Id:1start ...
Current thread Id:1enter ...
1111
Currret Thread Id:9start ...
Current thread Id:9enter ...
1111
2222
2222
3333
3333
4444
4444
5555
Current thread id:1out ...
5555
Current thread id:9out ...

4.wait (), notify ()----call wait or notify, the thread must be the owner of the lock on the object, or it will throw a exception in thread "Thread-0" Java.lang.IllegalMonitorStateException

New Thread (New Runnable () {public            void run () {                System.out.println ("------");                Synchronized (lock) {                    try {                        thread.sleep],                    } catch (Interruptedexception e) {                        e.printstacktrace ( );                    }                    Lock.notify ();                    System.out.println ("After notify ...");}}        ). Start ();        Synchronized (lock) {            System.out.println ("Enter ...");            Lock.wait ();            System.out.println ("Out ...");        

Results:

Enter ...
------
After notify ...
Out ...

5.wait (), Notifyall ()----notifyall () wakes up all the different threads in wait

    New Thread (New Runnable () {public void run () {synchronized (lock) {Sys                    Tem.out.println ("Enter thread 1 ...");                    try {lock.wait ();                    } catch (Interruptedexception e) {e.printstacktrace ();                } System.out.println ("Leave thread 1 ...");        }}). Start (); New Thread (New Runnable () {public void run () {synchronized (lock) {System.                    Out.println ("Enter thread 2 ...");                    try {lock.wait ();                    } catch (Interruptedexception e) {e.printstacktrace ();                } System.out.println ("Leave thread 2 ...");        }}). Start (); New Thread (New Runnable () {public void run () {System.out.priNTLN ("------");                    Synchronized (lock) {try {thread.sleep (3000);                    } catch (Interruptedexception e) {e.printstacktrace ();                    } lock.notifyall ();//The Notifyall method wakes all threads that are waiting for control of the object.                Lock.notify ();//randomly notifies a waiting thread System.out.println ("after notifyall ..."); }}). Start ();

Results:

Enter Thread 1 ...
Enter Thread 2 ...
------
After Notifyall ...
Leave thread 2 ...
Leave thread 1 ...

6.static synchronization methods, different objects

Thread current = Thread.CurrentThread ();        System.out.println ("Currret thread ID:" + current.getid () + "start ...");        Sync sync = new sync ();        New Thread (New Runnable () {public            void run () {                sync sync = new sync ();                Thread current = Thread.CurrentThread ();                System.out.println ("Currret thread ID:" + current.getid () + "start ...");                try {                    sync.staticsync ();//Lock valid/                    /Sync.staticsync ();//Lock valid                    //Sync.sync ();//Lock Invalid                } catch ( Interruptedexception e) {                    e.printstacktrace ();}}}        ). Start ();        Sync.staticsync ();//Lock valid        //Sync.staticsync ();//Lock valid        //Sync.sync ();//Lock invalid

Results:

Currret Thread Id:1start ...
Current thread Id:1enter ...
1111
Currret Thread Id:9start ...
2222
3333
4444
5555
Current thread id:1out ...
Current thread Id:9enter ...
1111
2222
3333
4444
5555
Current thread id:9out ...

7.class synchronization methods, different objects

Thread current = Thread.CurrentThread ();        System.out.println ("Currret thread ID:" + current.getid () + "start ...");        Sync sync = new sync ();        New Thread (New Runnable () {public            void run () {                sync sync = new sync ();                Thread current = Thread.CurrentThread ();                System.out.println ("Currret thread ID:" + current.getid () + "start ...");                try {                    sync.classsync ();//Lock valid                } catch (Interruptedexception e) {                    e.printstacktrace ();}}}        ). Start ();        Sync.classsync ();//Lock valid

Results:

Currret Thread Id:1start ...
Current thread Id:1enter ...
1111
Currret Thread Id:9start ...
2222
3333
4444
5555
Current thread id:1out ...
Current thread Id:9enter ...
1111
2222
3333
4444
5555
Current thread id:9out ...

8.this synchronous method, different objects, like 2, Object lock

Final Sync sync = new sync ();                New Thread (New Runnable () {public void run () {//sync Sync =new sync ();                Thread current = Thread.CurrentThread ();                System.out.println ("Currret thread ID:" + current.getid () + "start ...");                try {sync.thissync ();                } catch (Interruptedexception e) {e.printstacktrace ();        }}). Start ();                New Thread (New Runnable () {public void run () {//sync Sync =new sync ();                Thread current = Thread.CurrentThread ();                System.out.println ("Currret thread ID:" + current.getid () + "start ...");                try {sync.thissync ();                } catch (Interruptedexception e) {e.printstacktrace (); }}). Start ();

Results:

Currret Thread Id:9start ...
Current thread Id:9enter ...
1111
Currret Thread Id:10start ...
2222
3333
4444
5555
Current thread id:9out ...
Current thread Id:10enter ...
1111
2222
3333
4444
5555
Current thread id:10out ...

Java synchronization Mechanism object lock usage Comparison