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package main

import "fmt"

func main() {
	c := make(chan int)        // 不是一个名为chan类型为int的参数，而是一个Channel类型: chan int
	fmt.Printf("type:%T\n", c) //type:chan int
	// 看上去，Channel实际上是一个Pointer？
	fmt.Printf("value:%v\n", c) // value:0xc820078060
}

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package main

import "fmt"

func main() {
	v1 := 1
	v2 := &v1
	v3 := &v2
	v4 := &v2
	v5 := &v4

liufor

package main
import "fmt"

func main() {
        c := make(chan bool)
        m := make(map[string]string)
        go func() {
                m["1"] = "a" // First conflicting access.
                c <- true
        }()

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import com.mysql.jdbc.MySQLConnection;
import java.sql.*;
import java.util.concurrent.TimeUnit;

/**
 * MySQL 默认可重复读RR.
 * 两个线程T1，T2 分别执行一个业务单元.
 * T1中先 UPDATE test1 set field1='AA' where id=1, 然后 select field1 from test1 where id=1就应该返回 AA.
 * T2同理, set BB 后，select出的也应该是 BB .
 * <p>

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import java.io.IOException;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.concurrent.TimeUnit;

public class SimultaneousOpenConnectionEstablishment {
  
  private static int port1 = 18081;
    private static int port2 = 18082;
  

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import java.util.WeakHashMap;
import java.util.concurrent.TimeUnit;

/**
 * 展示会引起 MemoryLeak 的 WeakHashMap 错误用法: value 引用了 key.
 * <ul>
 * <li>
 * 1、 java.util.WeakHashMap 的 key (String类型） 在没有 strongly reachable 时，就会被自动回收。
 * <li>
 * 2、 key、value会组成一个 WeakReference 的子类 Entry（继承不是WeakReference的必备），但 referent object 仅仅包括 key. 所以：

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import java.util.concurrent.*;

public class QueuesTaskExecuteLaterDemo {
    public static void main(String[] args) throws InterruptedException {
        ArrayBlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(90);
        ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 10,
            5, TimeUnit.SECONDS, workQueue);

        executor.allowCoreThreadTimeOut(true);

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import java.util.concurrent.*;

public class AddWorkerDemo {
    public static void main(String[] args) throws InterruptedException {
        ArrayBlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(190);
        ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 10,
            190, TimeUnit.SECONDS, workQueue);

        Runnable r = new Runnable() {
            @Override

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2018-12-11 17:42:41
Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.111-b14 mixed mode):

"HikariPool-1 connection closer" #26929 daemon prio=5 os_prio=0 tid=0x00007f06f8b06000 nid=0x6940 waiting on condition [0x00007f06d2e2e000]
   java.lang.Thread.State: TIMED_WAITING (parking)
	at sun.misc.Unsafe.park(Native Method)
	- parking to wait for  <0x00000000c470e670> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
	at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:215)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2078)
	at java.util.concurrent.LinkedBlockingQueue.poll(LinkedBlockingQueue.java:467)

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public class MainObjectLong {
    public static void main(String[] args) {
        try {

            System.out.println(Object.test42());
            System.out.println(Long.test43());
            System.out.println("success:加载的是自定义的 Object/Long");

        } catch (Exception ex) {
            System.out.println("exception:");