[英]Executor System.out.println not showing in console
package com.company;
import java.io.Console;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;
public class Main {
static boolean isToastShewnLeft = false;
public static void main(String[] args) {
showToastLeft("first", "", "");
showToastLeft("second", "", "");
showToastLeft("third", "", "");
showToastLeft("fourth", "", "");
showToastLeft("fifth", "", "");
}
public static void showToastLeft(final String paramToastString1, final String paramToastString2, final String paramToastString3) {
final long start = System.currentTimeMillis();
ScheduledExecutorService worker1 = Executors.newSingleThreadScheduledExecutor();
ScheduledExecutorService worker2 = Executors.newSingleThreadScheduledExecutor();
if (isToastShewnLeft) {
final Runnable r = new Runnable() {
@SuppressWarnings("StatementWithEmptyBody")
public void run() {
while (isToastShewnLeft) {
}
isToastShewnLeft = true;
//This line does not appear in console output
//I can set a breakpoint on this println and see that it does execute
System.out.println(paramToastString1);
ScheduledExecutorService worker3 = Executors.newSingleThreadScheduledExecutor();
final Runnable r2 = new Runnable() {
public void run() {
isToastShewnLeft = false;
System.out.println(System.currentTimeMillis() - start + " Set toast not shewn");
}
};
worker3.schedule(r2, 5, TimeUnit.SECONDS);
}
};
worker1.schedule(r, 0, TimeUnit.SECONDS);
} else {
isToastShewnLeft = true;
System.out.println(paramToastString1);
final Runnable r2 = new Runnable() {
public void run() {
isToastShewnLeft = false;
System.out.println(System.currentTimeMillis() - start + " Set toast not shewn");
}
};
worker2.schedule(r2, 5, TimeUnit.SECONDS);
}
}
}
/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/bin/java -Didea.launcher.port=7543 "-Didea.launcher.bin.path=/Applications/IntelliJ IDEA 14 CE.app/Contents/bin" -Dfile.encoding=UTF-8 -classpath "/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/javafx-doclet.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/lib/tools.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/htmlconverter.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.7.0_75.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Users/ericsepich/IdeaProjects/untitled1/out/production/untitled1:/Applications/IntelliJ IDEA 14 CE.app/Contents/lib/idea_rt.jar" com.intellij.rt.execution.application.AppMain com.company.Main
first
5008 Set toast not shewn
我的目的是在每次调用 showToastLeft 时显示间隔 5 秒的文本。 从执行程序线程使用 println 是否可能存在问题? 我使用 IntelliJ idea 作为我的 IDE。
我将发布一个屏幕截图,显示我的调试器中布尔值的值为真。
感谢您的任何回应......
您不会让 Java 线程系统有机会在您的线程之间共享 CPU。
while (isToastShewnLeft) {
// Add this.
Thread.sleep(10);
}
您有多个线程在没有任何并发保护的情况下读取和写入isToastShewnLeft
变量。 尝试将isToastShewnLeft
上的所有读/写操作isToastShewnLeft
在synchronized
,看看这是否有所不同。 这里的问题可能是与线程相关的可见性问题:线程保留自己的变量副本并重新排序操作以提高效率的微妙情况。 同步是防止任何共享变量发生这种情况的一种方法。 这是对可见性的一个很好的解释, 这是另一个。
除了synchronized
,您还可以使用java.util.concurrent.AtomicBoolean
,如果假设您真的很关心性能(考虑到 5 秒的间隔,我对此表示怀疑)。 您是否可以通过将isToastShewnLeft
变成一个volatile
变量来逃避,这有点主观,但鉴于isToastShewnLeft
的状态会影响写入它的内容,我会回避这一点。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.