使我的处理器达到峰值的方法

Question

可能的重复：
如何开始优化我的 Java 代码？ - CPU 处于 100%

我有一个方法 isReset() ，它执行得像我

   public boolean isReset() { return reset; 
   }

在另一个类中定义的那样疯狂。 下面的类是唯一使用此代码的类。

import java.awt.BorderLayout;
import java.awt.Dimension;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.KeyEvent;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.IOException;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.KeyStroke;
import javax.swing.border.BevelBorder;
import javax.swing.border.SoftBevelBorder;


// TimerQueue

public class SkaTest {
   public static final int WIDTH = 500;
   public static final int HEIGHT = 500;
   public static final int CANVAS_X = 100;
   public static final int CANVAS_Y = 100;
   public static final int CANVAS_FRAME_WIDTH = WIDTH+100;
   public static final int CANVAS_FRAME_HEIGHT = HEIGHT + 100;
   public static final int EXEC_WIDTH = 550;
   public static final int EXEC_HEIGHT = 400;

   static VizDSList dsList = new VizDSList();
   static SkaCanvas canvas = new SkaCanvas(dsList);
   static JFrame canvasFrame = new JFrame("Data Structure Canvas");
   static JMenuBar menuBar = new JMenuBar();
   static JMenu algorithmMenu = new JMenu("Algorithm");
   static JMenu dsMenu = new JMenu("Create");
   static JMenu helpMenu = new JMenu ("Help");
   static JLabel status = new JLabel(" ");   

   static SkaProgram[] alg;
   static JFrame execFrame[];
   static SkaExecutionPanel execPanel[];


   public static void setupFrames(int nAlgs) {
      int i; 

      for (i=0; i < nAlgs; i++) {
         // execFrame[i] = new JFrame("Execution Control Panel "+(i+1));
         execFrame[i] = new JFrame();
         execPanel[i] = new SkaExecutionPanel(execFrame[i]);
      }

      canvas.setMinimumSize(new Dimension(WIDTH, HEIGHT));
      canvasFrame.setSize(CANVAS_FRAME_WIDTH, CANVAS_FRAME_WIDTH);
      canvasFrame.getContentPane().setLayout(new BorderLayout(10,7));
      // canvasFrame.getContentPane().setPreferredSize(new Dimension(WIDTH, HEIGHT));
      canvasFrame.addWindowListener(new WindowAdapter() {
         public void windowClosing(WindowEvent e) {
            System.exit(0);
         }
      });
      // canvas.setMinimumSize(new Dimension(WIDTH, HEIGHT));

      for (i=0; i < nAlgs; i++) {
         execFrame[i].setSize(EXEC_WIDTH, EXEC_HEIGHT);
         // execFrame[i].getContentPane().setLayout(new BorderLayout(10,7));
         execFrame[i].addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
               System.exit(0);
            }
         });
         execPanel[i].setBorder(new SoftBevelBorder(BevelBorder.RAISED));
         // execFrame[i].setContentPane(execPanel[i]);
         execFrame[i].getContentPane().add("Center", execPanel[i]);
         // execFrame[i].setLocation(CANVAS_X +CANVAS_FRAME_WIDTH, CANVAS_Y + i*EXEC_HEIGHT);
         execFrame[i].setLocation(CANVAS_X +CANVAS_FRAME_WIDTH + i*30, CANVAS_Y + i*50);
      }

      canvas.setBorder(new SoftBevelBorder(BevelBorder.RAISED));
      canvasFrame.getContentPane().add("Center", new JScrollPane(canvas) );
      // canvasFrame.getContentPane().add("Center", new JScrollPane(canvas, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS, ScrollPaneConstants.HORIZONTAL_SCROLLBAR_ALWAYS) );
      canvasFrame.getContentPane().add("South", status);
      canvasFrame.setLocation(CANVAS_X, CANVAS_Y);

      JMenu fileMenu = new JMenu("File");
      JMenuItem quitItem = new JMenuItem("Quit");
      //TODO Add quit listener
      quitItem.addActionListener(new ActionListener ()
      {


        public void actionPerformed(ActionEvent arg0) {
            //System.exit(0);

            int again = JOptionPane.showConfirmDialog(null, "Are you sure you want to exit system", "Exiting", JOptionPane.YES_NO_OPTION);
            if (again == JOptionPane.YES_OPTION)
            {
                System.exit(0);
            }


        }

      }
      );
      fileMenu.add(quitItem);
      menuBar.add(fileMenu);
      menuBar.add(algorithmMenu);
     // menuBar.add(dsMenu);
      menuBar.add(helpMenu);
      JMenuItem help = new JMenuItem ("Help Contents");
      //help.setMnemonic(KeyEvent.VK_H);
      //TODO Fix this method
      help.setAccelerator(KeyStroke.getKeyStroke(KeyEvent.VK_F1, ActionEvent.CTRL_MASK));
      help.addActionListener(new ActionListener()
      {
/*
        @Override
        public void actionPerformed(ActionEvent arg0) {
            JOptionPane.showMessageDialog(null, "Alot of the functionality have not yet been included in this version\nCurrently working on the automation features now!", "SKA 0.2 Beta", JOptionPane.WARNING_MESSAGE);

        }
*/

        public void actionPerformed(ActionEvent arg0) {
            try {
                Runtime.getRuntime().exec("hh.exe C:/ska.chm");
            } catch (IOException e) {
                e.printStackTrace();
                JOptionPane.showMessageDialog(null, "File not found", "Error", JOptionPane.ERROR_MESSAGE);
            }


        }

      });
      JMenuItem about = new JMenuItem ("About SKA");
      about.addActionListener(new ActionListener(){


        public void actionPerformed(ActionEvent arg0) {
        JOptionPane.showMessageDialog(null, "SKA Version 0.1 Beta");

        }
    });
      helpMenu.add(help);
      helpMenu.add(about);
      canvasFrame.setJMenuBar(menuBar);
   }

   /** The create menu item  */
   public static void createProgram(int i) {
      JMenuItem algItem;
      switch (i) {
      case 0 :
          alg[0] = new RedBlackValidate(canvas, execPanel[0]);
          execFrame[0].setTitle("Validate Algorithm");
          System.out.println("Validate Algorithm");
          algItem = new JMenuItem("Validate Algorithm");
          algorithmMenu.add(algItem);
          break;
      default:
         break;         
      }
   }


   public static void main(String args[]) {
      int i, nAlgs = 1; //nAlgs = 7;

      alg = new SkaProgram[nAlgs];
      execPanel = new SkaExecutionPanel[nAlgs];
      execFrame = new JFrame[nAlgs];

      // canvas.setDebugGraphicsOptions(DebugGraphics.BUFFERED_OPTION);
      setupFrames(nAlgs);
      canvasFrame.setVisible(true);


      for (i=0; i < alg.length; i++) {
         createProgram(i);
         execFrame[i].setVisible(true);
         alg[i].start();
         alg[i].displayAlgorithm();
      }

      while (true) {
         for (i=0; i < alg.length; i++) 
            if (execPanel[i].isReset()) {
               alg[i].terminate();
               createProgram(i);
               alg[i].start();
               execPanel[i].unreset();
            }         
      }
   }
}  // End class SkaTest

Answer 1

isReset 没有任何问题，但是这个循环不会一遍又一遍地调用它（一遍又一遍......）吗？

 while (true) {
     for (i=0; i < alg.length; i++) 
        if (execPanel[i].isReset()) {
           alg[i].terminate();
           createProgram(i);
           alg[i].start();
           execPanel[i].unreset();
        }         
  }

如果不出意外，您可以在其中添加一个 Thread.yield() 来强制线程定期放弃其时间片，这样它就不会占用 CPU。

更好的方法是放弃轮询，而使用基于侦听器的方法。 允许 execPanel 在重置时通知侦听器，而不是让一个循环反复询问它们是否已重置。 这段代码相当于“我们到了吗？我们到了吗？我们到了吗？”

您可能还会看到被称为观察者的侦听器。 如果您四处寻找有关此设计模式的更多信息，将会有很多有用的信息使用这两个术语出现。

示例

以下是您可以如何重写代码以使用侦听器概念。 对于这段代码中的任何错误，我深表歉意，我还没有编译它。 尽管代码中可能存在任何错误，但希望这些想法是清晰的。

如果代码立即没有意义，请查看我上面的链接。 或者您可以使用 EventListener s，当您进行 Swing GUI 编程时，您将一直使用它。

public class SkaExecutionPanel {
    // Anybody who wants to be told when a panel is reset will implement
    // this interface and call addListener().
    public interface Listener {
        void panelReset(SkaExecutionPanel panel);
    }

    // Each panel needs to maintain an internal list of listeners.
    private List<Listener> listeners = new ArrayList<Listener>();

    public void addListener(Listener listener) {
        listeners.add(listener);
    }

    public void removeListener(Listener listener) {
        listeners.remove(listener);
    }

    public void reset() {
        /* Do your thing. */

        // When something happens that the listeners will care about, such as a
        // call to reset() in this case, you iterate through the list and tell
        // each one what's happened.
        for (Listener listener: listeners) {
            listener.panelReset(this);
        }
    }
}

public class SkaTest {
    public static void main(String args[]) {
        /* Snippety snip. */

        for (i=0; i < alg.length; i++) {
            // Here we need to tell the execPanels that we want to do something
            // whenever somebody calls reset() on them. We will add a listener
            // to each panel that does the terminate/createProgram/start dance.
            // This way we don't have to ask the panels when they are reset; 
            // instead they will tell us when that happens.
            execPanel[i].addListener(new SkaExecutionPanel.Listener() {
                final int index = i;

                public void panelReset(SkaExecutionPanel panel) {
                    alg[index].terminate();
                    createProgram(index);
                    alg[index].start();
                    execPanel[index].unreset();
                }
            });
        }
    }
}

Answer 2

这是添加此信息后对我对第一个问题的回答的编辑：

“编辑： while 循环是一个无限循环，导致 for 循环运行，其中已检查数组中的每个项目以查看其是否已重置您可以用观察者模式替换它，当对象重置时，它会通知观察对象，然后执行该组步骤，这样您就不会出现无限循环，并且可以减少 .isReset( 的使用。 ）”。

编辑：其他答案的问题是，在我看来，使用无限循环有点代码味道。

编辑2：这是带有示例的维基百科文章。