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4、LockSupport与线程中断
2022-06-11 12:07:00 【施小赞】
1、线程中断机制
1.1、一道面试题
如何停止、中断一个运行中的线程？
1.2、什么是中断？
首先
一个线程不应该由其他线程来强制中断或停止，而是应该由线程自己自行停止。
所以，Thread.stop, Thread.suspend, Thread.resume 都已经被废弃了。
其次
在Java中没有办法立即停止一条线程，然而停止线程却显得尤为重要，如取消一个耗时操作。
因此，Java提供了一种用于停止线程的机制——中断。
中断只是一种协作机制，Java没有给中断增加任何语法，中断的过程完全需要程序员自己实现。
若要中断一个线程，你需要手动调用该线程的 interrupt 方法， 该方法也仅仅是将线程对象的中断标识设成true ；
接着你需要自己写代码不断地检测当前线程的标识位，如果为true，表示别的线程要求这条线程中断，
此时究竟该做什么需要你自己写代码实现。
每个线程对象中都有一个标识，用于表示线程是否被中断；该标识位为true表示中断，为false表示未中断；
通过调用线程对象的interrupt方法将该线程的标识位设为true；可以在别的线程中调用，也可以在自己的线程中调用。
1.3、中断的相关API方法
public void interrupt() | 实例方法， 实例方法interrupt()仅仅是设置线程的中断状态为true，不会停止线程 |
public static boolean interrupted() | 静态方法，Thread.interrupted(); 判断线程是否被中断，并清除当前中断状态 这个方法做了两件事： 1 返回当前线程的中断状态 2 将当前线程的中断状态设为false
这个方法有点不好理解，因为连续调用两次的结果可能不一样 。 |
public boolean isInterrupted() | 实例方法， 判断当前线程是否被中断（通过检查中断标志位） |
1.4、面试题：如何使用中断标识停止线程？
在需要中断的线程中不断监听中断状态，
一旦发生中断，就执行相应的中断处理业务逻辑。
修改状态
停止程序的运行。。。
1.4.1、方法
通过一个volatile变量实现
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
static volatile boolean isStop = false;
public static void main(String[] args) {
new Thread(() -> {
while (true) {
if (isStop) {
System.out.println("-----isStop = true，程序结束。");
break;
}
System.out.println("------hello isStop");
}
}, "t1").start();
//暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
isStop = true;
}, "t2").start();
}
}
返回结果：
------hello isStop
------hello isStop
------hello isStop
------hello isStop
------hello isStop
------hello isStop
-----isStop = true，程序结束。通过AtomicBoolean
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
static AtomicBoolean atomicBoolean = new AtomicBoolean(false);
public static void main(String[] args) {
new Thread(() -> {
while(true)
{
if(atomicBoolean.get())
{
System.out.println("-----atomicBoolean.get() = true，程序结束。");
break;
}
System.out.println("------hello atomicBoolean");
}
},"t1").start();
//暂停几秒钟线程
try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }
new Thread(() -> {
atomicBoolean.set(true);
},"t2").start();
}
}
返回结果：
------hello atomicBoolean
------hello atomicBoolean
------hello atomicBoolean
------hello atomicBoolean
------hello atomicBoolean
------hello atomicBoolean
------hello atomicBoolean
-----atomicBoolean.get() = true，程序结束。通过Thread类自带的中断api方法实现
实例方法interrupt()，没有返回值
源码分析：
实例方法isInterrupted，返回布尔值
源码分析：
code
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
public static void main(String[] args) {
Thread t1 = new Thread(() -> {
while (true) {
if (Thread.currentThread().isInterrupted()) {
System.out.println("-----isInterrupted() = true，程序结束。");
break;
}
System.out.println("------hello Interrupt");
}
}, "t1");
t1.start();
try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }
new Thread(() -> {
t1.interrupt();//修改t1线程的中断标志位为true
},"t2").start();
}
}
返回结果：
------hello Interrupt
------hello Interrupt
------hello Interrupt
------hello Interrupt
------hello Interrupt
------hello Interrupt
-----isInterrupted() = true，程序结束。1.4.2、当前线程的中断标识为true，是不是就立刻停止？
说明：
具体来说，当对一个线程，调用 interrupt() 时：
① 如果线程处于正常活动状态，那么会将该线程的中断标志设置为 true， 仅此而已 。
被设置中断标志的线程将继续正常运行，不受影响 。所以， interrupt() 并不能真正的中断线程，需要被调用的线程自己进行配合才行。
② 如果线程处于被阻塞状态（例如处于sleep, wait, join 等状态），在别的线程中调用当前线程对象的interrupt方法，
那么线程将立即退出被阻塞状态，并抛出一个InterruptedException异常。
code1
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
public static void main(String[] args) {
//中断为true后，并不是立刻stop程序
Thread t1 = new Thread(() -> {
for (int i = 1; i <= 300; i++) {
System.out.println("------i: " + i);
}
System.out.println("t1.interrupt()调用之后02： "+Thread.currentThread().isInterrupted());
}, "t1");
t1.start();
System.out.println("t1.interrupt()调用之前,t1线程的中断标识默认值： "+t1.isInterrupted());
try { TimeUnit.MILLISECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); }
//实例方法interrupt()仅仅是设置线程的中断状态位设置为true，不会停止线程
t1.interrupt();
//活动状态,t1线程还在执行中
System.out.println("t1.interrupt()调用之后01： "+t1.isInterrupted());
try { TimeUnit.MILLISECONDS.sleep(3000); } catch (InterruptedException e) { e.printStackTrace(); }
//非活动状态,t1线程不在执行中，已经结束执行了。
System.out.println("t1.interrupt()调用之后03： "+t1.isInterrupted());
}
}运行结果
/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=61077:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/tools.jar:/Users/shishizan/2022-java/大厂JUC/代码/juc2021/target/classes:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.4.3/spring-boot-starter-web-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter/2.4.3/spring-boot-starter-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.4.3/spring-boot-starter-logging-2.4.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar:/Users/shishizan/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar:/Users/shishizan/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar:/Users/shishizan/.m2/repository/org/yaml/snakeyaml/1.27/snakeyaml-1.27.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.4.3/spring-boot-starter-json-2.4.3.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.4/jackson-databind-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.4/jackson-annotations-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.4/jackson-core-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.4/jackson-datatype-jdk8-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.4/jackson-datatype-jsr310-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.4/jackson-module-parameter-names-2.11.4.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.4.3/spring-boot-starter-tomcat-2.4.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.43/tomcat-embed-core-9.0.43.jar:/Users/shishizan/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.43/tomcat-embed-websocket-9.0.43.jar:/Users/shishizan/.m2/repository/org/springframework/spring-web/5.3.4/spring-web-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-beans/5.3.4/spring-beans-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-webmvc/5.3.4/spring-webmvc-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-aop/5.3.4/spring-aop-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-context/5.3.4/spring-context-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-expression/5.3.4/spring-expression-5.3.4.jar:/Users/shishizan/.m2/repository/org/openjdk/jol/jol-core/0.9/jol-core-0.9.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-devtools/2.4.3/spring-boot-devtools-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot/2.4.3/spring-boot-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.4.3/spring-boot-autoconfigure-2.4.3.jar:/Users/shishizan/.m2/repository/org/projectlombok/lombok/1.18.18/lombok-1.18.18.jar:/Users/shishizan/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar:/Users/shishizan/.m2/repository/org/springframework/spring-core/5.3.4/spring-core-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-jcl/5.3.4/spring-jcl-5.3.4.jar com.atguigu.juc.interrupt.InterruptDemoCopy
t1.interrupt()调用之前,t1线程的中断标识默认值： false
------i: 1
------i: 2
------i: 3
------i: 4
------i: 5
------i: 6
------i: 7
------i: 8
------i: 9
------i: 10
------i: 11
------i: 12
------i: 13
。。。。。。
------i: 218
------i: 219
------i: 220
------i: 221
------i: 222
------i: 223
t1.interrupt()调用之后01： true
------i: 224
------i: 225
------i: 226
------i: 227
------i: 228
------i: 229
。。。。。。
------i: 298
------i: 299
------i: 300
t1.interrupt()调用之后02： true
t1.interrupt()调用之后03： false
Process finished with exit code 0code2
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
public static void main(String[] args) {
Thread t1 = new Thread(() -> {
while (true) {
if (Thread.currentThread().isInterrupted()) {
System.out.println("-----isInterrupted() = true，程序结束。");
break;
}
try {
Thread.sleep(500);
} catch (InterruptedException e) {
Thread.currentThread().interrupt();//??????? //线程的中断标志位为false,无法停下，需要再次掉interrupt()设置true
e.printStackTrace();
}
System.out.println("------hello Interrupt");
}
}, "t1");
t1.start();
try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); }
new Thread(() -> {
t1.interrupt();//修改t1线程的中断标志位为true
},"t2").start();
}
}
返回结果
/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=63044:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/tools.jar:/Users/shishizan/2022-java/大厂JUC/代码/juc2021/target/classes:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.4.3/spring-boot-starter-web-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter/2.4.3/spring-boot-starter-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.4.3/spring-boot-starter-logging-2.4.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar:/Users/shishizan/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar:/Users/shishizan/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar:/Users/shishizan/.m2/repository/org/yaml/snakeyaml/1.27/snakeyaml-1.27.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.4.3/spring-boot-starter-json-2.4.3.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.4/jackson-databind-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.4/jackson-annotations-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.4/jackson-core-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.4/jackson-datatype-jdk8-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.4/jackson-datatype-jsr310-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.4/jackson-module-parameter-names-2.11.4.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.4.3/spring-boot-starter-tomcat-2.4.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.43/tomcat-embed-core-9.0.43.jar:/Users/shishizan/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.43/tomcat-embed-websocket-9.0.43.jar:/Users/shishizan/.m2/repository/org/springframework/spring-web/5.3.4/spring-web-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-beans/5.3.4/spring-beans-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-webmvc/5.3.4/spring-webmvc-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-aop/5.3.4/spring-aop-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-context/5.3.4/spring-context-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-expression/5.3.4/spring-expression-5.3.4.jar:/Users/shishizan/.m2/repository/org/openjdk/jol/jol-core/0.9/jol-core-0.9.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-devtools/2.4.3/spring-boot-devtools-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot/2.4.3/spring-boot-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.4.3/spring-boot-autoconfigure-2.4.3.jar:/Users/shishizan/.m2/repository/org/projectlombok/lombok/1.18.18/lombok-1.18.18.jar:/Users/shishizan/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar:/Users/shishizan/.m2/repository/org/springframework/spring-core/5.3.4/spring-core-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-jcl/5.3.4/spring-jcl-5.3.4.jar com.atguigu.juc.interrupt.InterruptDemoCopy
------hello Interrupt
------hello Interrupt
------hello Interrupt
------hello Interrupt
------hello Interrupt
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.atguigu.juc.interrupt.InterruptDemoCopy.lambda$main$0(InterruptDemoCopy.java:20)
at java.lang.Thread.run(Thread.java:748)
------hello Interrupt
-----isInterrupted() = true，程序结束。
Process finished with exit code 0
结论：
sleep方法抛出InterruptedException后，中断标识也被清空置为false，我们在catch没有通过调用Thread.currentThread().interrupt();方法再次将中断表示置为true，这就导致无限循环了
小总结：
中断只是一种协同机制，修改中断标识位仅此而已，不是立刻stop打断
1.4.2、静态方法Thread.interrupted()
静态方法Thread.interrupted()：
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicBoolean;
/**
* @auther zzyy
* @create 2021-03-03 18:20
*/
public class InterruptDemoCopy {
public static void main(String[] args) {
System.out.println(Thread.currentThread().getName() + "---" + Thread.interrupted());
System.out.println(Thread.currentThread().getName() + "---" + Thread.interrupted());
System.out.println("111111");
/* 作用是测试当前线程是否被中断（检查中断标志），返回一个 boolean 并清除中断状态，
* 第二次再调用时中断状态已经被清除，将返回一个 false 。
*/
Thread.currentThread().interrupt();///----false---> true
System.out.println("222222");
System.out.println(Thread.currentThread().getName() + "---" + Thread.interrupted());
System.out.println(Thread.currentThread().getName() + "---" + Thread.interrupted());
}
}
返回结果：
/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/bin/java -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=65487:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_251.jdk/Contents/Home/lib/tools.jar:/Users/shishizan/2022-java/大厂JUC/代码/juc2021/target/classes:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-web/2.4.3/spring-boot-starter-web-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter/2.4.3/spring-boot-starter-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-logging/2.4.3/spring-boot-starter-logging-2.4.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-classic/1.2.3/logback-classic-1.2.3.jar:/Users/shishizan/.m2/repository/ch/qos/logback/logback-core/1.2.3/logback-core-1.2.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-to-slf4j/2.13.3/log4j-to-slf4j-2.13.3.jar:/Users/shishizan/.m2/repository/org/apache/logging/log4j/log4j-api/2.13.3/log4j-api-2.13.3.jar:/Users/shishizan/.m2/repository/org/slf4j/jul-to-slf4j/1.7.30/jul-to-slf4j-1.7.30.jar:/Users/shishizan/.m2/repository/jakarta/annotation/jakarta.annotation-api/1.3.5/jakarta.annotation-api-1.3.5.jar:/Users/shishizan/.m2/repository/org/yaml/snakeyaml/1.27/snakeyaml-1.27.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-json/2.4.3/spring-boot-starter-json-2.4.3.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-databind/2.11.4/jackson-databind-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-annotations/2.11.4/jackson-annotations-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/core/jackson-core/2.11.4/jackson-core-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jdk8/2.11.4/jackson-datatype-jdk8-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/datatype/jackson-datatype-jsr310/2.11.4/jackson-datatype-jsr310-2.11.4.jar:/Users/shishizan/.m2/repository/com/fasterxml/jackson/module/jackson-module-parameter-names/2.11.4/jackson-module-parameter-names-2.11.4.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-starter-tomcat/2.4.3/spring-boot-starter-tomcat-2.4.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-core/9.0.43/tomcat-embed-core-9.0.43.jar:/Users/shishizan/.m2/repository/org/glassfish/jakarta.el/3.0.3/jakarta.el-3.0.3.jar:/Users/shishizan/.m2/repository/org/apache/tomcat/embed/tomcat-embed-websocket/9.0.43/tomcat-embed-websocket-9.0.43.jar:/Users/shishizan/.m2/repository/org/springframework/spring-web/5.3.4/spring-web-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-beans/5.3.4/spring-beans-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-webmvc/5.3.4/spring-webmvc-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-aop/5.3.4/spring-aop-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-context/5.3.4/spring-context-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-expression/5.3.4/spring-expression-5.3.4.jar:/Users/shishizan/.m2/repository/org/openjdk/jol/jol-core/0.9/jol-core-0.9.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-devtools/2.4.3/spring-boot-devtools-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot/2.4.3/spring-boot-2.4.3.jar:/Users/shishizan/.m2/repository/org/springframework/boot/spring-boot-autoconfigure/2.4.3/spring-boot-autoconfigure-2.4.3.jar:/Users/shishizan/.m2/repository/org/projectlombok/lombok/1.18.18/lombok-1.18.18.jar:/Users/shishizan/.m2/repository/org/slf4j/slf4j-api/1.7.30/slf4j-api-1.7.30.jar:/Users/shishizan/.m2/repository/org/springframework/spring-core/5.3.4/spring-core-5.3.4.jar:/Users/shishizan/.m2/repository/org/springframework/spring-jcl/5.3.4/spring-jcl-5.3.4.jar com.atguigu.juc.interrupt.InterruptDemoCopy
main---false
main---false
111111
222222
main---true
main---false
Process finished with exit code 0
静态方法与实例方法的对比
方法的注释也清晰的表达了“中断状态将会根据传入的ClearInterrupted参数值确定是否重置”。
所以，
静态方法interrupted将 会清除中断状态（传入的参数ClearInterrupted为true），
实例方法isInterrupted则不会（传入的参数ClearInterrupted为false）。
1.5、总结
线程中断相关的方法：
interrupt()方法是一个实例方法
它通知目标线程中断，也就是设置目标线程的中断标志位为true，中断标志位表示当前线程已经被中断了。
isInterrupted()方法也是一个实例方法
它判断当前线程是否被中断（通过检查中断标志位）并获取中断标志
Thread类的静态方法interrupted()
返回当前线程的中断状态(boolean类型)且将当前线程的中断状态设为false，此方法调用之后会清除当前线程的中断标志位的状态（将中断标志置为false了），返回当前值并清零置false
2、LockSupport是什么
LockSupport是用来创建锁和其他同步类的基本线程阻塞原语。
下面这句话，后面详细说
LockSupport中的park() 和 unpark() 的作用分别是阻塞线程和解除阻塞线程
3、线程等待唤醒机制
3.1、3种让线程等待和唤醒的方法
方式1：使用Object中的wait()方法让线程等待，使用Object中的notify()方法唤醒线程
方式2：使用JUC包中Condition的await()方法让线程等待，使用signal()方法唤醒线程
方式3：LockSupport类可以阻塞当前线程以及唤醒指定被阻塞的线程
3.2、Object类中的wait和notify方法实现线程等待和唤醒
正常代码：
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Object objectLock = new Object();
// 同一把锁，类似资源类
new Thread(() -> {
synchronized (objectLock) {
System.out.println(Thread.currentThread().getName()+"\t"+"---come in");
try {
objectLock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName() + " \t " + " 被唤醒了 ");
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
synchronized (objectLock) {
objectLock.notify();
System.out.println(Thread.currentThread().getName()+"\t"+"---发出通知");
}
}, "t2").start();
}
}
异常代码1：wait方法和notify方法，两个都去掉同步代码块
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Object objectLock = new Object();
// 同一把锁，类似资源类
new Thread(() -> {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
try {
objectLock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + " \t " + " 被唤醒了 ");
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
objectLock.notify();
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
}, "t2").start();
}
}
异常代码2：将notify放在wait方法前面，程序无法执行，无法唤醒
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Object objectLock = new Object();
// 同一把锁，类似资源类
new Thread(() -> {
synchronized (objectLock) {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
objectLock.notify();
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
}
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
synchronized (objectLock) {
try {
objectLock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
System.out.println(Thread.currentThread().getName() + " \t " + " 被唤醒了 ");
}, "t2").start();
}
} 
小总结：
- wait和notify方法必须要在同步块或者方法里面，且成对出现使用
- 先wait后notify才OK
3.3、Condition接口中的await后signal方法实现线程的等待和唤醒
正常代码：
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
new Thread(() -> {
lock.lock();
try {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
condition.await();
System.out.println(Thread.currentThread().getName() + "\t" + "---被唤醒");
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
lock.lock();
try {
condition.signal();
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
} finally {
lock.unlock();
}
}, "t2").start();
}
} 
异常代码1：去掉lock/unlock
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
new Thread(() -> {
try {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
condition.await();
System.out.println(Thread.currentThread().getName() + "\t" + "---被唤醒");
} catch (InterruptedException e) {
e.printStackTrace();
}
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
try {
condition.signal();
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
} catch (Exception e) {
e.printStackTrace();
}
}, "t2").start();
}
}
condition.await();和 condition.signal();都触发了 IllegalMonitorStateException异常。
结论：
lock、unlock对里面才能正确调用调用condition中线程等待和唤醒的方法
异常代码2：先signal后await
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
new Thread(() -> {
lock.lock();
try {
condition.signal();
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
} finally {
lock.unlock();
}
}, "t1").start();
// 暂停几秒钟线程
try {
TimeUnit.SECONDS.sleep(3L);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
lock.lock();
try {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
condition.await();
System.out.println(Thread.currentThread().getName() + "\t" + "---被唤醒");
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}, "t2").start();
}
}代码运行无法结束：线程无法被唤醒
小总结：
- Condtion中的线程等待和唤醒方法之前，需要先获取锁
- 一定要先await后signal，不要反了
3.4、Object和Condition使用的限制条件
线程先要获得并持有锁，必须在锁块(synchronized或lock)中
必须要先等待后唤醒，线程才能够被唤醒
3.5、LockSupport类中的park等待和unpark唤醒
3.5.1、是什么
通过park()和unpark(thread)方法来实现阻塞和唤醒线程的操作
官方解释：
LockSupport是用来创建锁和其他同步类的基本线程阻塞原语。
LockSupport类使用了一种名为Permit（许可）的概念来做到 阻塞和唤醒线程 的功能， 每个线程都有一个许可(permit)，
permit只有两个值1和零，默认是零。
可以把许可看成是一种(0,1)信号量（Semaphore），但与 Semaphore 不同的是，许可的累加上限是1。
3.5.2、主要方法
3.5.2.1、API
3.5.2.2、阻塞
park() /park(Object blocker)
调用 LockSupport. park ()时
permit默认是零，所以一开始调用park()方法，当前线程就会阻塞，直到别的线程将当前线程的permit设置为1时，park方法会被唤醒，
然后会将permit再次设置为零并返回。
阻塞当前线程/阻塞传入的具体线程
3.5.2.3、唤醒
unpark(Thread thread)
LockSupport. unpark (thread);
调用unpark(thread)方法后，就会将thread线程的许可permit设置成1(注意多次调用unpark方法，不会累加，permit值还是1)会自动唤醒thread线程，即之前阻塞中的LockSupport.park()方法会立即返回。
唤醒处于阻塞状态的指定线程
3.5.3、代码
3.5.3.1、正常+无锁块要求
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Thread t1 = new Thread(() -> {
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
LockSupport.park();
System.out.println(Thread.currentThread().getName() + "\t" + "---被唤醒");
}, "t1");
t1.start();
try { TimeUnit.SECONDS.sleep(3); } catch (InterruptedException e) { e.printStackTrace(); }
new Thread(() -> {
LockSupport.unpark(t1);
System.out.println(Thread.currentThread().getName()+"\t"+"---发出通知");
},"t2").start();
}
}
3.5.3.2、之前错误的先唤醒后等待，LockSupport照样支持
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Thread t1 = new Thread(() -> {
try {
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "\t" + System.currentTimeMillis() + "\t" + "---come in");
LockSupport.park();
System.out.println(Thread.currentThread().getName() + "\t" + System.currentTimeMillis() + "\t" + "---被唤醒");
}, "t1");
t1.start();
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
new Thread(() -> {
LockSupport.unpark(t1);
System.out.println(Thread.currentThread().getName() + "\t" + System.currentTimeMillis() + "\t" + "---发出通知");
}, "t2").start();
}
}
3.5.3.3、异常情况：没有考虑到 permit 上限值为 1
package com.atguigu.juc.interrupt;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.LockSupport;
import java.util.concurrent.locks.ReentrantLock;
/**
* @auther zzyy
* @create 2020-07-10 14:05
*/
public class LockSupportDemoCopy {
static Lock lock = new ReentrantLock();
static Condition condition = lock.newCondition();
public static void main(String[] args)//main 方法，主线程一切程序入口
{
Thread t1 = new Thread(() -> {
try {
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "\t" + "---come in");
LockSupport.park();
LockSupport.park();
System.out.println(Thread.currentThread().getName() + "\t" + "---被唤醒");
}, "t1");
t1.start();
new Thread(() -> {
LockSupport.unpark(t1);
LockSupport.unpark(t1);
System.out.println(Thread.currentThread().getName() + "\t" + "---发出通知");
}, "t2").start();
}
}程序运行结果：由于 permit 的上限值为 1，所以执行两次 LockSupport.park() 操作将导致 t1 线程阻塞
LockSupport和每个使用它的线程都有一个许可(permit)关联。permit相当于1，0的开关，默认是0，调用一次unpark就加1变成1，调用一次park会消费permit，也就是将1变成0，同时park立即返回。
如再次调用park会变成阻塞(因为permit为零了会阻塞在这里，一直到permit变为1)，这时调用unpark会把permit置为1。
每个线程都有一个相关的permit，permit最多只有一个，重复调用unpark也不会积累凭证。
线程阻塞需要消耗凭证(permit)，这个凭证最多只有1个。
1、当调用park方法时
如果有凭证，则会直接消耗掉这个凭证然后正常退出;
如果无凭证，就必须阻塞等待凭证可用;
2、而unpark则相反，它会增加一个凭证，但凭证最多只能有1个，累加无效。
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