[#0x004A] Java多线程:Runnable接口 v.s. Thread类

public class Runner implements Runnable {
	@Override
	public void run() {
		for(int i = 0; i < 100; i++) {
			System.out.println("Runner runs to --> " + i);
		}
	}
}

 

public class MultiThreadTest {

	public static void main(String[] args) {
		Runner r = new Runner();
		//r.run(); // 方法调用,没有启动新线程

		Thread t = new Thread(r);
		//t.run(); // 方法调用,没有启动新线程
		t.start(); // 启动新线程
		
		for(int i = 0; i < 200; i++) {
			System.out.println("Main goes " + i); 
		}
		
	}

}

 

Runnable接口和Thread类的关系:

 

1. 首先有Thread implememts Runnable

 

2.  虽说Runnable有一个方法run(),但基本上Runnable可以看做是一个标记接口;Runnable本身并不提供多线程机制,只有Thread类才能启动新线程;Runnable的实现类只有传递给Thread构造器才有意义

 

3.  Thread.run()默认会调用传递给Thread构造器的Runnable实现类的run(),如果没有Runnable实现类传进来的话,Thraed.run()方法什么都不做直接返回(可见Thread.run()是个空方法);但直接调用Thread.run()方法并不能启动新线程(直接调用Thread.run()方法相当于一般的方法调用,Runnable实现类的run()方法亦是如此),只有Thread.start()方法才能启动新线程;Thread.start()方法会调用Thread.run()方法

 

4.  定制自己的线程类的方法:

  -> class Runner implements Runnable,实现run()方法,然后Thread t = new Thread(new Ruuner()); t.start();

  -> class MyThread extends Thread覆写run()方法,然后MyThread mt = new MyThread(); mt.start();

  这两种方式又涉及到“接口还是继承”的设计原则问题了

 

我的javaSpringBoot程序线程dump中有大量线程阻塞到这里:"http-nio2-0.0.0.0-9798-exec-158" #3079 daemon prio=5 os_prio=0 tid=0x0000fff9d4001800 nid=0xabad9 waiting for monitor entry [0x0000fff9c07fc000] java.lang.Thread.State: BLOCKED (on object monitor) at sun.security.provider.SecureRandom.engineNextBytes(SecureRandom.java:215) - waiting to lock <0x00000001c9a639a8> (a sun.security.provider.SecureRandom) at java.security.SecureRandom.nextBytes(SecureRandom.java:468) at java.util.UUID.randomUUID(UUID.java:145) at com.jiuqi.common.base.util.UUIDUtils.newUUIDStr(UUIDUtils.java:34) at com.jiuqi.common.web.context.filter.BusinessContextDataFilter.getTraceId(BusinessContextDataFilter.java:59) at com.jiuqi.common.web.context.filter.BusinessContextDataFilter.doFilter(BusinessContextDataFilter.java:44) at com.tongweb.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) at com.tongweb.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at com.jiuqi.nvwa.sf.adapter.spring.SFFilter.doFilter(SFFilter.java:75) at com.tongweb.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) at com.tongweb.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165) at com.jiuqi.nvwa.sf.adapter.spring.MDCFilter.doFilter(MDCFilter.java:35) at com.tongweb.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192);持有锁的完整线程dump:"http-nio2-0.0.0.0-9798-exec-1" #24 daemon prio=5 os_prio=0 tid=0x0000fffc58df3000 nid=0xa9f4c runnable [0x0000fffc2c5cc000] java.lang.Thread.State: RUNNABLE at java.security.MessageDigest$Delegate.engineDigest(MessageDigest.java:592) at java.security.MessageDigest.digest(MessageDigest.java:365) at sun.security.provider.SecureRandom.engineNextBytes(SecureRandom.java:244) - locked <0x00000001c9a639a8> (a sun.security.provider.SecureRandom) at java.security.SecureRandom.nextBytes(SecureRandom.java:468) at java.util.UUID.randomUUID(UUID.java:145) at com.jiuqi.common.base.util.UUIDUtils.newUUIDStr(UUIDUtils.java:34) at com.jiuqi.common.web.context.filter.BusinessContextDataFilter.getTraceId(BusinessContextDataFilter.java:59) at com.jiuqi.common.web.context.filter.BusinessContextDataFilter.doFilter(BusinessContextDataFilter.java:44) at com.tongweb.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192) 可以帮我分析下吗?
07-13
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