JAVA之多线程优先级问题

最新推荐文章于 2022-06-14 14:02:59 发布

最新推荐文章于 2022-06-14 14:02:59 发布 · 57 阅读

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本文通过一个Java示例程序展示了线程优先级的实际效果。实验表明，线程优先级仅作为调度提示，不能确保高优先级线程一定先执行或获得更多CPU时间。文章中的程序创建了四个不同优先级的线程，并观察它们的执行顺序。

 线程优先级，并不能保证优先级高的先运行，也不保证优先级高的更多的分配CPU时间，只是对系统的建议而已，到底运行哪个，是操作系统决定的，都不是java说了算的。

优先级高就是说同等条件下我运行的概率会比优先级低的高，至于具体怎么分配，这样看虚拟机的策略。但是肯定不会是像你想的那样，优先级高的运行完才运行优先级低的

package Project;
import java.awt.*;
import javax.swing.*;

class CreateThread implements Runnable
{
	private int n = 0;
	private JProgressBar progressbar;
	private String str;
	public CreateThread(JProgressBar progressbar, String str)
	{
		this.progressbar = progressbar;
		this.str = str;
	}
	public void run()
	{
		n = 0;
		while(true)
		{
			try{
				Thread.sleep(5000);
			}catch(Exception e)
			{
				e.printStackTrace();
			}
			progressbar.setValue(n++);
			System.out.println(str);
			if(n == 101)
				break;
		}
	}
}

public class Project1 extends JFrame
{
	/**
	 * 
	 */
	private static final long serialVersionUID = -8798841678332294307L;
	public void setProgressBar(JProgressBar progressbar, Container container)
	{
		progressbar.setStringPainted(true);
		container.add(progressbar);
	}
	public Project1()
	{
		super("进程");
		Container container = getContentPane();
		container.setBackground(Color.white);
		container.setLayout(new GridLayout(4, 1, 10, 10));
		
		final JProgressBar progressbar1 = new JProgressBar();
		setProgressBar(progressbar1, container);
		Thread thread1 = new Thread(new CreateThread(progressbar1, "progressbar1"));
		thread1.setPriority(1);
		thread1.start();
		
		final JProgressBar progressbar2 = new JProgressBar();
		setProgressBar(progressbar2, container);
		Thread thread2 = new Thread(new CreateThread(progressbar2, "progressbar2"));
		thread2.setPriority(7);
		thread2.start();
		
		final JProgressBar progressbar3 = new JProgressBar();
		setProgressBar(progressbar3, container);
		Thread thread3 = new Thread(new CreateThread(progressbar3, "progressbar3"));
		thread3.setPriority(4);
		thread3.start();
		
		final JProgressBar progressbar4 = new JProgressBar();
		setProgressBar(progressbar4, container);
		Thread thread4 = new Thread(new CreateThread(progressbar4, "progressbar4"));
		thread4.setPriority(10);
		thread4.start();
		
	}
	public static void draw(JFrame jframe, int width, int height)
	{
		jframe.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
		jframe.setVisible(true);
		jframe.setBounds(300, 300, width, height);
	}
	public static void main (String []args)
	{
		draw(new Project1(), 300, 300);
	}
}

运行结果：

progressbar2
progressbar4
progressbar1
progressbar3
progressbar2
progressbar4
progressbar3
progressbar1
progressbar2
progressbar4
progressbar3
progressbar1
progressbar2
progressbar4
progressbar3
progressbar1
progressbar2
progressbar4
progressbar3
progressbar1