文章目录
静态同步synchronized方法与synchronized(class)代码块
package multiply.com.test;
public class Run {
public static void main(String[] args) {
Service service = new Service();
//同一个类，不同的对象
ThreadA aThread = new ThreadA(service);
ThreadB bThread = new ThreadB(service);
ThreadC cThread = new ThreadC(service);
aThread.setName("A");
bThread.setName("B");
cThread.setName("C");
aThread.start();
bThread.start();
cThread.start();
}
}
package multiply.com.test;
public class ThreadA extends Thread {
private Service service;
public ThreadA(Service service) {
this.service = service;
}
@Override
public void run() {
super.run();
service.printA();
}
}
package multiply.com.test;
public class ThreadB extends Thread {
private Service service;
public ThreadB(Service service) {
this.service = service;
}
@Override
public void run() {
super.run();
service.printB();
}
}
package multiply.com.test;
public class ThreadC extends Thread {
private Service service;
public ThreadC(Service service) {
this.service = service;
}
@Override
public void run() {
super.run();
service.printC();
}
}
package multiply.com.test;
public class Service {
synchronized public static void printA() {
try {
System.out.println("thread name = " + Thread.currentThread().getName() + " in printA at " + System.currentTimeMillis());
Thread.sleep(3000);
System.out.println("thread name = " + Thread.currentThread().getName() + " out printA at " + System.currentTimeMillis());
} catch (InterruptedException e) {
e.printStackTrace();
}
}
synchronized public static void printB() {
System.out.println("thread name = " + Thread.currentThread().getName() + " in printB at " + System.currentTimeMillis());
System.out.println("thread name = " + Thread.currentThread().getName() + " out printB at " + System.currentTimeMillis());
}
synchronized public void printC() {
System.out.println("thread name = " + Thread.currentThread().getName() + " in printC at " + System.currentTimeMillis());
System.out.println("thread name = " + Thread.currentThread().getName() + " out printC at " + System.currentTimeMillis());
}
}
thread name = C in printC at 1634869837541
thread name = A in printA at 1634869837541
thread name = C out printC at 1634869837541
thread name = A out printA at 1634869840542
thread name = B in printB at 1634869840542
thread name = B out printB at 1634869840542
A和B是类锁，是并行的。C是对象锁是和A串行的。
数据类型String的常量池特性
package multiply.com.test;
public class Run {
public static void main(String[] args) {
ThreadA aThread = new ThreadA();
ThreadB bThread = new ThreadB();
aThread.setName("A");
bThread.setName("B");
aThread.start();
bThread.start();
}
}
package multiply.com.test;
public class ThreadA extends Thread {
@Override
public void run() {
super.run();
Service.print("AA");
}
}
package multiply.com.test;
public class ThreadB extends Thread {
@Override
public void run() {
super.run();
Service.print("AA");
}
}
package multiply.com.test;
public class Service {
public static void print(String stringParam) {
try {
synchronized (stringParam) {
while (true) {
System.out.println(Thread.currentThread().getName());
Thread.sleep(1000);
}
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
B
B
B
B…
多线程的死锁
package multiply.com.test;
public class Run {
public static void main(String[] args) {
try {
DealThread t1 = new DealThread();
t1.setFlag("a");
Thread thread1 = new Thread(t1);
thread1.start();
Thread.sleep(100);
t1.setFlag("b");
Thread thread2 = new Thread(t1);
thread2.start();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
package multiply.com.test;
public class DealThread implements Runnable {
public String username;
public Object lock1 = new Object();
public Object lock2 = new Object();
public void setFlag(String username) {
this.username = username;
}
@Override
public void run() {
if ("a".equals(username)) {
synchronized (lock1) {
try {
System.out.println("username = " + username);
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lock2) {
System.out.println("lock1 -> lock2");
}
}
}
if ("b".equals(username)) {
synchronized (lock2) {
try {
System.out.println("username = " + username);
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lock1) {
System.out.println("lock2 -> lock1");
}
}
}
}
}
内置类与静态内置类
package multiply.com.test;
public class Run {
public static void main(String[] args) {
final OutClass.Inner inner = new OutClass.Inner();
Thread t1 = new Thread(new Runnable() {
@Override
public void run() {
inner.method1();
}
}, "A");
Thread t2 = new Thread(new Runnable() {
@Override
public void run() {
inner.method2();
}
}, "B");
t1.start();
t2.start();
}
}
package multiply.com.test;
public class OutClass {
static class Inner {
public void method1() {
synchronized ("其他的锁") {
for (int i = 0; i < 10; i++) {
System.out.println(Thread.currentThread().getName() + " i = " + i);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
public synchronized void method2() {
for (int i = 11; i < 20; i++) {
System.out.println(Thread.currentThread().getName() + " i = " + i);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
volatile关键字
解决同步死循环
package multiply.com.test;
public class Run {
public static void main(String[] args) throws InterruptedException {
PrintString printStringService = new PrintString();
new Thread(printStringService).start();
System.out.println("I want to stop it ! stop thread = " + Thread.currentThread().getName());
printStringService.setContinuePrint(false);
}
}
package multiply.com.test;
public class PrintString implements Runnable {
private boolean isContinuePrint = true;
public boolean isContinuePrint() {
return isContinuePrint;
}
public void setContinuePrint(boolean isContinuePrint) {
this.isContinuePrint = isContinuePrint;
}
public void printStringMethod() {
try {
while (isContinuePrint == true) {
System.out.println("run printStringMethod thread name = " + Thread.currentThread().getName());
Thread.sleep(1000);
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
@Override
public void run() {
printStringMethod();
}
}
I want to stop it ! stop thread = main
run printStringMethod thread name = Thread-0
package multiply.com.test;
public class Run {
public static void main(String[] args) {
try {
RunThread thread = new RunThread();
thread.start();
Thread.sleep(1000);
thread.setRunning(false);
System.out.println("isRunning is set by false");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
package multiply.com.test;
public class RunThread extends Thread {
volatile private boolean isRunning = true;
public boolean isRunning() {
return isRunning;
}
public void setRunning(boolean isRunning) {
this.isRunning = isRunning;
}
@Override
public void run() {
super.run();
System.out.println("in run method ");
while (isRunning == true) {
}
System.out.println("end run method");
}
}
in run method
isRunning is set by false
end run method
synchronized代码块具有volatile数据同步功能
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package multiply.com.test;
public class Run {
public static void main(String[] args) throws InterruptedException {
Service service = new Service();
ThreadA a = new ThreadA(service);
a.start();
Thread.sleep(1000);
ThreadB b = new ThreadB(service);
b.start();
System.out.println("had been stopped !");
}
}
package multiply.com.test;
public class ThreadA extends Thread{
private Service service;
public ThreadA(Service service) {
this.service = service;
}
@Override
public void run() {
super.run();
service.runMethod();
}
}
package multiply.com.test;
public class ThreadB extends Thread {
Service service;
public ThreadB(Service service) {
this.service = service;
}
@Override
public void run() {
super.run();
service.stopMethod();
}
}
package multiply.com.test;
public class Service {
private boolean isContinueRun = true;
synchronized public void runMethod() {
String anyString = new String();
while (true == isContinueRun) {
synchronized (anyString) {
}
}
System.out.println("stopped!");
}
public void stopMethod() {
isContinueRun = false;
}
}
had been stopped !
stopped!
