Thread Synchronization reason and Method

We know that using the runnable method to implement threads can achieve resource sharing, but there are still problems. refer to the following code:

// Reason for synchronization <br/> class mythread implements runnable <br/>{< br/> private int ticket = 10; <br/> Public void run () {<br/> for (INT I = 0; I <100; I ++) {<br/> If (ticket> 0) {<br/> try {<br/> thread. sleep (2000); // when this statement is added, there will be a delay, resulting in the resource exceeding the usage range <br/>} catch (interruptedexception e) {}< br/> system. out. println (thread. currentthread (). getname () + "ticket selling:" + ticket --); <br/>}< br/> public class syncdemo01 <br/>{< br/> Public static void main (string ARGs []) {<br/> mythread my = new mythread (); <br/> thread a = new thread (my, ""); <br/> thread B = new thread (my, "B"); <br/> thread c = new thread (my, "C"); <br/>. start (); <br/> B. start (); <br/> C. start (); <br/>}< br/>}

 

When there is a delay, it may cause resource sharing errors. So we need to use synchronization to solve this problem. There are two ways to implement synchronization: Use the synchronized code block and the synchronized method.

First, let's look at the first method, using the synchronized code block:

// Use synchronized to synchronize code blocks <br/> class mythread implements runnable <br/>{< br/> private int ticket = 10; <br/> Public void run () {<br/> for (INT I = 0; I <100; I ++) {</P> <p> synchronized (this) {// Synchronous Code block <br/> If (ticket> 0) {<br/> try {<br/> thread. sleep (500); // when this statement is added, there will be a delay, resulting in the resource exceeding the usage range <br/>} catch (interruptedexception e) {}< br/> system. out. println (thread. currentthread (). getname () + "ticket selling:" + ticket --); <br/>}< br/> public class syncdemo02 <br/>{< br/> Public static void main (string ARGs []) {<br/> mythread my = new mythread (); <br/> thread a = new thread (my, ""); <br/> thread B = new thread (my, "B"); <br/> thread c = new thread (my, "C"); <br/>. start (); <br/> B. start (); <br/> C. start (); <br/>}< br/>}

We can see through running that the problem can be well solved. At the same time, you can view the preemption and switching between processes through multiple running.

Let's take a look at the second implementation method, using the synchronized method:

// Use the Synchronized Method for synchronization <br/> class mythread implements runnable <br/>{< br/> private int ticket = 10; <br/> Public void run () {<br/> for (INT I = 0; I <100; I ++) {<br/> This. fun (); <br/>}< br/> Public synchronized void fun () {<br/> If (ticket> 0) {<br/> try {<br/> thread. sleep (500); // when this statement is added, there will be a delay, resulting in the resource exceeding the usage range <br/>} catch (interruptedexception e) {}< br/> system. out. println (thread. currentthread (). getname () + "ticket selling:" + ticket --); <br/>}< br/> public class syncdemo03 <br/>{< br/> Public static void main (string ARGs []) {<br/> mythread my = new mythread (); <br/> thread a = new thread (my, ""); <br/> thread B = new thread (my, "B"); <br/> thread c = new thread (my, "C"); <br/>. start (); <br/> B. start (); <br/> C. start (); <br/>}< br/>}

Through running, you can find that this method can also solve the problem. When this is done, I have a question: if you use the Synchronized Method for synchronization, the run method is also a method. Can you set the run method to a synchronous method. To solve this problem, try the following:

// Set the run method as the synchronization method <br/> class mythread implements runnable <br/>{< br/> private int ticket = 10; <br/> Public synchronized void run () {<br/> for (INT I = 0; I <100; I ++) {<br/> If (ticket> 0) {<br/> try {<br/> thread. sleep (1000); // when this statement is added, there will be a delay, resulting in the resource exceeding the usage range <br/>} catch (interruptedexception e) {}< br/> system. out. println (thread. currentthread (). getname () + "ticket selling:" + ticket --); <br/>}</P> <p >}< br/> public class syncdemo04 <br/>{< br/> Public static void main (string ARGs []) {<br/> mythread my = new mythread (); <br/> thread a = new thread (my, ""); <br/> thread B = new thread (my, "B"); <br/> thread c = new thread (my, "C"); <br/>. start (); <br/> B. start (); <br/> C. start (); <br/>}< br/>}

If it is still successful after running, is there a problem? What are the differences between the synchronized code block and the synchronized method? The above code is a thread implemented by implementing the runnable interface. Can the thread implemented by inheriting the thread be synchronized?