notify 在这篇文章中,我们将看到 Java和Java 之间的区别notifyall 。
通知():
当您在对象上调用notify]方法时,它会唤醒等待该对象的线程之一。因此,如果多个线程正在等待一个对象,它将唤醒其中一个。现在你一定想知道它会唤醒哪一个。它实际上取决于操作系统的实现。
通知所有():
notifyAll 将唤醒等待该对象的所有线程,不像 notify 只唤醒其中一个。哪个将首先唤醒取决于线程优先级和操作系统实现。
让我们借助示例来理解它:
1. 创建一个名为 File.java 的类:
线程将在其上执行操作并调用等待和通知方法是 java bean 类。
package org.arpit.java2blog.thread;
public class File {
String name;
boolean isCompleted;
public File(String name) {
super();
this.name = name;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public boolean isCompleted() {
return isCompleted;
}
public void setCompleted(boolean isCompleted) {
this.isCompleted = isCompleted;
}
}
2. 创建一个名为 FileReader.java 的类
这个线程会一直等到其他线程调用notify方法,然后才会完成它的处理。它将首先锁定文件对象,并从同步块中调用。因此在此示例中,它将等待 FileWriter 完成文件。
package org.arpit.java2blog.thread;
public class FileReader implements Runnable{
File file;
public FileReader(File file) {
super();
this.file = file;
}
@Override
public void run() {
synchronized (file) {
System.out.println(Thread.currentThread().getName()+" is waiting for the file to be completed: "+file.getName());
try {
file.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName()+": File has been completed now!! you can read it");
}
}
}
3. 创建一个名为 FileWriter.java 的类
此类将通知正在等待文件对象的线程(在通知的情况下)。它不会在调用 notify 后立即放弃锁,它首先完成其同步块。所以在本例中,FileWriter 将完成文件并将其通知给 FileReaders。
package org.arpit.java2blog.thread;
public class FileWriter implements Runnable{
File file;
public FileWriter(File file) {
super();
this.file = file;
}
@Override
public void run() {
synchronized (file) {
System.out.println("Write is going to start writing the file : " +file.getName() );
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
file.setCompleted(true);
System.out.println("File has been completed now");
file.notify();
System.out.println("notify one reader");
}
}
}
4. 创建类NotifyAndNotifyAllMain,java。
这是我们的主类,它将创建上述类的对象并运行它。
package org.arpit.java2blog.thread;
public class NotifyAndNotifyAllMain {
public static void main(String args[])
{
// File object on which wait and notify method will be called
File file=new File("Excel file");
FileReader reader1=new FileReader(file);
FileReader reader2=new FileReader(file);
// FileReader threads which will wait for completion of file
Thread thread1=new Thread(reader1,"Reader 1");
Thread thread2=new Thread(reader2,"Reader 2");
thread2.start();
thread1.start();
// To ensure both readers started waiting for the file
try {
Thread.sleep(3000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// FileWriter thread which will notify once file get completed
FileWriter fileWriter=new FileWriter(file);
Thread fileWriterThread=new Thread(fileWriter);
fileWriterThread.start();
}
}
在通知()的情况下:
当您运行上述程序时,您将获得以下输出:
Reader 2 is waiting for the file to be completed: Excel file
Reader 1 is waiting for the file to be completed: Excel file
Write is going to start writing the file : Excel file
File has been completed now
notify one reader
Reader 2: File has been completed now!! you can read it
所以在这里,两个 FileReader 线程(阅读器 1 和阅读器 2)正在等待文件完成,所以他们调用了 file.wait()。一旦 FileWriter 完成它的文件,它就会调用 file.notify() 并且 reader 2 线程启动并完成其处理。
在 notifyAll() 的情况下:
让我们将 FileWriter 类更改为调用 file.notifyAll()。
package org.arpit.java2blog.thread;
public class FileWriter implements Runnable{
File file;
public FileWriter(File file) {
super();
this.file = file;
}
@Override
public void run() {
synchronized (file) {
System.out.println("Write is going to start writing the file : " +file.getName() );
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
file.setCompleted(true);
System.out.println("File has been completed now");
file.notifyAll();
System.out.println("notify all readers");
}
}
}
当你运行上面的程序时,你会得到以下输出:
Reader 2 is waiting for the file to be completed: Excel file
Reader 1 is waiting for the file to be completed: Excel file
Write is going to start writing the file : Excel file
File has been completed now
notify all readers
Reader 1: File has been completed now!! you can read it
Reader 2: File has been completed now!! you can read it
在 notifyAll() 的情况下,它会通知所有等待该对象的线程。
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