线程池——ThreadPoolExecutor
1.创建线程的方式?
2.为什么使用线程池？有什么优势？
3.线程池的3个常用方式？
4.线程池的7大参数？
5.线程池底层工作原理？
6.线程池的拒绝策略？
7.线程池工作原理的代码验证？
public static void main(String[] args) throws Exception { // 创建核心线程数2,最大线程数5,阻塞队列size=3的线程池 ThreadPoolExecutor threadPoolExecutor = new ThreadPoolExecutor(2, 5, 2, TimeUnit.SECONDS, new LinkedBlockingDeque<>(3), Executors.defaultThreadFactory(), new ThreadPoolExecutor.AbortPolicy()); for (int i = 1; i <= 9; i++) { final int finalI = i; try { threadPoolExecutor.execute(() -> { System.out.print("【" + finalI + "】"); try { Thread.sleep(2000); } catch (Exception e) { e.printStackTrace(); } }); } catch (Exception e) { System.out.print("【异常】"); } Thread.sleep(20); } }
8.线程池配置合理的参数？N代表cpu核心数
CPU密集：大量的运算，IO操作时间短，CPU Loading比较高
IO密集：大部分状况是CPU在等待IO读写操作，CPU Loading较低
9.死锁编码及定位分析？使用 jstack [pid] 命令
public class Demo { public static void main(String[] args) { String resourceA = "lockA"; String resourceB = "lockB"; new Thread(() -> { synchronized (resourceA) { System.out.println(Thread.currentThread().getName()+"\t: 拥有资源A,尝试获取资源B"); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } synchronized (resourceB) { } } }, "线程A").start(); new Thread(() -> { synchronized (resourceB) { System.out.println(Thread.currentThread().getName()+"\t: 拥有资源B,尝试获取资源A"); try { Thread.sleep(1000); } catch (InterruptedException e) { e.printStackTrace(); } synchronized (resourceA) { } } }, "线程B").start(); } }
D:\project\idea\demo>jps -l 20656 org.jetbrains.jps.cmdline.Launcher 9204 1356 org.jetbrains.idea.maven.server.RemoteMavenServer36 16364 sun.tools.jps.Jps 5804 锁.手写一个死锁.Demo D:\project\idea\demo>jstack 5804 2022-02-10 13:48:02 Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.311-b11 mixed mode): "DestroyJavaVM" #22 prio=5 os_prio=0 tid=0x0000020580bb9800 nid=0x51e4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "线程B" #21 prio=5 os_prio=0 tid=0x000002059ebe1800 nid=0x4240 waiting for monitor entry [0x0000003f12fff000] java.lang.Thread.State: BLOCKED (on object monitor) at 锁.手写一个死锁.Demo.lambda$main$1(Demo.java:20) - waiting to lock <0x000000076be246d0> (a java.lang.String) - locked <0x000000076be24708> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$2/1078694789.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "线程A" #20 prio=5 os_prio=0 tid=0x000002059ebdc800 nid=0x1d8c waiting for monitor entry [0x0000003f12eff000] java.lang.Thread.State: BLOCKED (on object monitor) at 锁.手写一个死锁.Demo.lambda$main$0(Demo.java:12) - waiting to lock <0x000000076be24708> (a java.lang.String) - locked <0x000000076be246d0> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$1/990368553.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "Service Thread" #19 daemon prio=9 os_prio=0 tid=0x000002059e80f800 nid=0x9fc runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread11" #18 daemon prio=9 os_prio=2 tid=0x000002059e753000 nid=0x53f4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread10" #17 daemon prio=9 os_prio=2 tid=0x000002059e752800 nid=0x16c0 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread9" #16 daemon prio=9 os_prio=2 tid=0x000002059e74f800 nid=0x2dac waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread8" #15 daemon prio=9 os_prio=2 tid=0x000002059e754000 nid=0x1200 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread7" #14 daemon prio=9 os_prio=2 tid=0x000002059e751800 nid=0x2ff4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread6" #13 daemon prio=9 os_prio=2 tid=0x000002059e750000 nid=0x1a98 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread5" #12 daemon prio=9 os_prio=2 tid=0x000002059e74e800 nid=0x4cb4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread4" #11 daemon prio=9 os_prio=2 tid=0x000002059e755800 nid=0x4e80 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x000002059e751000 nid=0x4a80 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000002059e74c000 nid=0x1140 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000002059e749000 nid=0x4eb4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000002059e746800 nid=0x106c waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000002059e745000 nid=0x4548 runnable [0x0000003f11ffe000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:171) at java.net.SocketInputStream.read(SocketInputStream.java:141) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178) - locked <0x000000076bd0fcd0> (a java.io.InputStreamReader) at java.io.InputStreamReader.read(InputStreamReader.java:184) at java.io.BufferedReader.fill(BufferedReader.java:161) at java.io.BufferedReader.readLine(BufferedReader.java:324) - locked <0x000000076bd0fcd0> (a java.io.InputStreamReader) at java.io.BufferedReader.readLine(BufferedReader.java:389) at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:61) "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000002059e6ea000 nid=0x1b50 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000002059e6d6000 nid=0x5178 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000002059baab800 nid=0x3a4 in Object.wait() [0x0000003f11cfe000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000076bb88ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144) - locked <0x000000076bb88ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216) "Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x000002059e6b2800 nid=0x1640 in Object.wait() [0x0000003f11bfe000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000076bb86c00> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x000000076bb86c00> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) "VM Thread" os_prio=2 tid=0x000002059baa5800 nid=0x2cdc runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000020580bd2800 nid=0x14f8 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000020580bd3800 nid=0x2244 runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000020580bd5000 nid=0x3884 runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000020580bd6800 nid=0x160c runnable "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x0000020580bd8800 nid=0x3bfc runnable "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x0000020580bd9800 nid=0x34f4 runnable "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x0000020580bdc800 nid=0x5070 runnable "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x0000020580bdd800 nid=0x424c runnable "GC task thread#8 (ParallelGC)" os_prio=0 tid=0x0000020580bde800 nid=0x50d4 runnable "GC task thread#9 (ParallelGC)" os_prio=0 tid=0x0000020580be0000 nid=0x409c runnable "GC task thread#10 (ParallelGC)" os_prio=0 tid=0x0000020580be1000 nid=0x4610 runnable "GC task thread#11 (ParallelGC)" os_prio=0 tid=0x0000020580be4000 nid=0x52b8 runnable "GC task thread#12 (ParallelGC)" os_prio=0 tid=0x0000020580be6000 nid=0x5364 runnable "VM Periodic Task Thread" os_prio=2 tid=0x000002059e86f800 nid=0x5250 waiting on condition JNI global references: 316 Found one Java-level deadlock: ============================= "???程B": waiting to lock monitor 0x000002059b6c7598 (object 0x000000076be246d0, a java.lang.String), which is held by "线??A" "线程A": waiting to lock monitor 0x000002059b6c4d08 (object 0x000000076be24708, a java.lang.String), which is held by "线程B" Java stack information for the threads listed above: =================================================== "线程B": at 锁.手写一个死锁.Demo.lambda$main$1(Demo.java:20) - waiting to lock <0x000000076be246d0> (a java.lang.String) - locked <0x000000076be24708> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$2/1078694789.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "线程A": at 锁.手写一个死锁.Demo.lambda$main$0(Demo.java:12) - waiting to lock <0x000000076be24708> (a java.lang.String) - locked <0x000000076be246d0> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$1/990368553.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) Found 1 deadlock. D:\project\idea\demo>clear 'clear' 不是内部或外部命令，也不是可运行的程序 或批处理文件。 D:\project\idea\demo>cls D:\project\idea\demo>jps -l 20656 org.jetbrains.jps.cmdline.Launcher 9204 20040 sun.tools.jps.Jps 1356 org.jetbrains.idea.maven.server.RemoteMavenServer36 5804 锁.手写一个死锁.Demo D:\project\idea\demo>jstack 5804 2022-02-10 13:57:23 Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.311-b11 mixed mode): "DestroyJavaVM" #22 prio=5 os_prio=0 tid=0x0000020580bb9800 nid=0x51e4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "线程B" #21 prio=5 os_prio=0 tid=0x000002059ebe1800 nid=0x4240 waiting for monitor entry [0x0000003f12fff000] java.lang.Thread.State: BLOCKED (on object monitor) at 锁.手写一个死锁.Demo.lambda$main$1(Demo.java:20) - waiting to lock <0x000000076be246d0> (a java.lang.String) - locked <0x000000076be24708> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$2/1078694789.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "线程A" #20 prio=5 os_prio=0 tid=0x000002059ebdc800 nid=0x1d8c waiting for monitor entry [0x0000003f12eff000] java.lang.Thread.State: BLOCKED (on object monitor) at 锁.手写一个死锁.Demo.lambda$main$0(Demo.java:12) - waiting to lock <0x000000076be24708> (a java.lang.String) - locked <0x000000076be246d0> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$1/990368553.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "Service Thread" #19 daemon prio=9 os_prio=0 tid=0x000002059e80f800 nid=0x9fc runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread11" #18 daemon prio=9 os_prio=2 tid=0x000002059e753000 nid=0x53f4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread10" #17 daemon prio=9 os_prio=2 tid=0x000002059e752800 nid=0x16c0 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread9" #16 daemon prio=9 os_prio=2 tid=0x000002059e74f800 nid=0x2dac waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread8" #15 daemon prio=9 os_prio=2 tid=0x000002059e754000 nid=0x1200 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread7" #14 daemon prio=9 os_prio=2 tid=0x000002059e751800 nid=0x2ff4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread6" #13 daemon prio=9 os_prio=2 tid=0x000002059e750000 nid=0x1a98 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread5" #12 daemon prio=9 os_prio=2 tid=0x000002059e74e800 nid=0x4cb4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread4" #11 daemon prio=9 os_prio=2 tid=0x000002059e755800 nid=0x4e80 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread3" #10 daemon prio=9 os_prio=2 tid=0x000002059e751000 nid=0x4a80 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread2" #9 daemon prio=9 os_prio=2 tid=0x000002059e74c000 nid=0x1140 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread1" #8 daemon prio=9 os_prio=2 tid=0x000002059e749000 nid=0x4eb4 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "C2 CompilerThread0" #7 daemon prio=9 os_prio=2 tid=0x000002059e746800 nid=0x106c waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Monitor Ctrl-Break" #6 daemon prio=5 os_prio=0 tid=0x000002059e745000 nid=0x4548 runnable [0x0000003f11ffe000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.socketRead(SocketInputStream.java:116) at java.net.SocketInputStream.read(SocketInputStream.java:171) at java.net.SocketInputStream.read(SocketInputStream.java:141) at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:284) at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:326) at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:178) - locked <0x000000076bd0fcd0> (a java.io.InputStreamReader) at java.io.InputStreamReader.read(InputStreamReader.java:184) at java.io.BufferedReader.fill(BufferedReader.java:161) at java.io.BufferedReader.readLine(BufferedReader.java:324) - locked <0x000000076bd0fcd0> (a java.io.InputStreamReader) at java.io.BufferedReader.readLine(BufferedReader.java:389) at com.intellij.rt.execution.application.AppMainV2$1.run(AppMainV2.java:61) "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000002059e6ea000 nid=0x1b50 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000002059e6d6000 nid=0x5178 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x000002059baab800 nid=0x3a4 in Object.wait() [0x0000003f11cfe000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000076bb88ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:144) - locked <0x000000076bb88ee0> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:165) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:216) "Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x000002059e6b2800 nid=0x1640 in Object.wait() [0x0000003f11bfe000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x000000076bb86c00> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference.tryHandlePending(Reference.java:191) - locked <0x000000076bb86c00> (a java.lang.ref.Reference$Lock) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153) "VM Thread" os_prio=2 tid=0x000002059baa5800 nid=0x2cdc runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000020580bd2800 nid=0x14f8 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000020580bd3800 nid=0x2244 runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000020580bd5000 nid=0x3884 runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000020580bd6800 nid=0x160c runnable "GC task thread#4 (ParallelGC)" os_prio=0 tid=0x0000020580bd8800 nid=0x3bfc runnable "GC task thread#5 (ParallelGC)" os_prio=0 tid=0x0000020580bd9800 nid=0x34f4 runnable "GC task thread#6 (ParallelGC)" os_prio=0 tid=0x0000020580bdc800 nid=0x5070 runnable "GC task thread#7 (ParallelGC)" os_prio=0 tid=0x0000020580bdd800 nid=0x424c runnable "GC task thread#8 (ParallelGC)" os_prio=0 tid=0x0000020580bde800 nid=0x50d4 runnable "GC task thread#9 (ParallelGC)" os_prio=0 tid=0x0000020580be0000 nid=0x409c runnable "GC task thread#10 (ParallelGC)" os_prio=0 tid=0x0000020580be1000 nid=0x4610 runnable "GC task thread#11 (ParallelGC)" os_prio=0 tid=0x0000020580be4000 nid=0x52b8 runnable "GC task thread#12 (ParallelGC)" os_prio=0 tid=0x0000020580be6000 nid=0x5364 runnable "VM Periodic Task Thread" os_prio=2 tid=0x000002059e86f800 nid=0x5250 waiting on condition JNI global references: 316 Found one Java-level deadlock: ============================= "???程B": waiting to lock monitor 0x000002059b6c7598 (object 0x000000076be246d0, a java.lang.String), which is held by "线??A" "线程A": waiting to lock monitor 0x000002059b6c4d08 (object 0x000000076be24708, a java.lang.String), which is held by "线程B" Java stack information for the threads listed above: =================================================== "线程B": at 锁.手写一个死锁.Demo.lambda$main$1(Demo.java:20) - waiting to lock <0x000000076be246d0> (a java.lang.String) - locked <0x000000076be24708> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$2/1078694789.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) "线程A": at 锁.手写一个死锁.Demo.lambda$main$0(Demo.java:12) - waiting to lock <0x000000076be24708> (a java.lang.String) - locked <0x000000076be246d0> (a java.lang.String) at 锁.手写一个死锁.Demo$$Lambda$1/990368553.run(Unknown Source) at java.lang.Thread.run(Thread.java:748) Found 1 deadlock.
===END===
作者：[一柒微笑]
