孔维滢 20171010110《面向对象程序设计（java）》第九周学习总结

package 异常;

//异常示例1
public class ExceptionDemo1 {
    public static void main(String args[]) {
        int a=0;
        if(a==0) {
            System.out.println("除数不能为零！");
        }
        else {
            System.out.println(5 / a);

        }
    }
}

import java.io.*;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class ExceptionDemo2 {
    public static void main(String args[]) throws IOException 
     {
          try {

          File file = new File("text.txt");
          FileInputStream fis = new FileInputStream(file);
          BufferedReader in = new BufferedReader(new InputStreamReader(fis));
          String b;
          while((b=in.readLine())!=null)
          {
              System.out.print(b);
          }
          fis.close();
      }catch (Exception e) {
          e.printStackTrace();
      }
     }
}

package stackTrace;

import java.util.*;

/**
 * A program that displays a trace feature of a recursive method call.
 * @version 1.01 2004-05-10
 * @author Cay Horstmann
 */
public class StackTraceTest
{
   /**
    * Computes the factorial of a number
    * @param n a non-negative integer
    * @return n! = 1 * 2 * . . . * n
    */
   public static int factorial(int n)
   {
      System.out.println("factorial(" + n + "):");
      Throwable t = new Throwable();
      StackTraceElement[] frames = t.getStackTrace();
      for (StackTraceElement f : frames)
         System.out.println(f);
      int r;
      if (n <= 1) r = 1;
      else r = n * factorial(n - 1);
      System.out.println("return " + r);
      return r;
   }

   public static void main(String[] args)
   {
      Scanner in = new Scanner(System.in);
      System.out.print("Enter n: ");
      int n = in.nextInt();
      factorial(n);
   }
}

package 计算器;

import java.util.Scanner;
import java.util.Random;
import java.io.FileNotFoundException;
import java.io.PrintWriter;

public class Exam{
    int sum;
    public static void main(String[] args) {
        Exam exam = new Exam();
        exam.sum = 0;
        Random r = new Random ();
        PrintWriter output = null;
        try {
            output = new PrintWriter("E://text.txt");
        } catch (Exception e) {
        }

        for(int i = 0;i<10;i++) {
            exam.score();
        }
        System.out.println("你的总分为："+exam.sum);
        output.close();
    }
    private void score() {
        Random r = new Random ();
        int m;
        m  = (int) Math.round(Math.random() * 4);
        switch(m) {
        case 0:
            int a,b,c;
            a = r.nextInt() % 100;
            b = r.nextInt() % 100;
            System.out.println(a + "+" + "(" + b + ")=");
            Scanner x = new Scanner(System.in);
            c = x.nextInt();
            if(c != a+b)
                System.out.println("答案错误！");
            else {
                System.out.println("答案正确！");
                sum += 10;
            }
            break;
        case 1:
            int o,p,q;
            o = r.nextInt() % 100;
            p = r.nextInt() % 100;
            System.out.println(o + "-" + "(" + p + ")=");
            Scanner y = new Scanner(System.in);
            q = y.nextInt();
            if(q != o-p)
                System.out.println("答案错误！");
            else {
                System.out.println("答案正确！");
                sum += 10;
            }
            break;
        case 2:
            int d,e,f;
            d = r.nextInt() % 100;
            e = r.nextInt() % 100;
            System.out.println(d + "*" +"("+ e + ")" + "=");
            Scanner z = new Scanner(System.in);
            f = z.nextInt();
            if(f != d * e)
            System.out.println("答案错误！");
            else {
                System.out.println("答案正确！");
                sum += 10;
            }
            break;
        case 3:
            int h,i,j;
            h = r.nextInt() % 100;
            i = r.nextInt() % 100;
            if(i == 0)
                i++;
            System.out.println(h + "/" +"("+ i + ")" + "=");
            Scanner u = new Scanner(System.in);
            j = u.nextInt();
            if(j != h/i)
                System.out.println("答案错误！");
            else {
                System.out.println("答案正确！");
                sum += 10;
            }
            break;
        }
    }
}

//断言程序示例
public class AssertDemo {
    public static void main(String[] args) {        
        //test1(-5);
        test2(-3);
    }
    
    private static void test1(int a){
        assert a > 0;
        System.out.println(a);
    }
    private static void test2(int a){
       assert a > 0 : "something goes wrong here, a cannot be less than 0";
        System.out.println(a);
    }
}

package logging;

import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.logging.*;
import javax.swing.*;

/**
 * A modification of the image viewer program that logs various events.
 * @version 1.03 2015-08-20
 * @author Cay Horstmann
 */
public class LoggingImageViewer
{
   public static void main(String[] args)
   {
      if (System.getProperty("java.util.logging.config.class") == null
            && System.getProperty("java.util.logging.config.file") == null)
      {
         try
         {
            Logger.getLogger("com.horstmann.corejava").setLevel(Level.ALL);
            final int LOG_ROTATION_COUNT = 10;
            Handler handler = new FileHandler("%h/LoggingImageViewer.log", 0, LOG_ROTATION_COUNT);
            Logger.getLogger("com.horstmann.corejava").addHandler(handler);
         }
         catch (IOException e)
         {
            Logger.getLogger("com.horstmann.corejava").log(Level.SEVERE,
                  "Can‘t create log file handler", e);
         }
      }

      EventQueue.invokeLater(() ->
            {
               Handler windowHandler = new WindowHandler();
               windowHandler.setLevel(Level.ALL);
               Logger.getLogger("com.horstmann.corejava").addHandler(windowHandler);

               JFrame frame = new ImageViewerFrame();
               frame.setTitle("LoggingImageViewer");
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

               Logger.getLogger("com.horstmann.corejava").fine("Showing frame");
               frame.setVisible(true);
            });
   }
}

/**
 * The frame that shows the image.
 */
class ImageViewerFrame extends JFrame
{
   private static final int DEFAULT_WIDTH = 300;
   private static final int DEFAULT_HEIGHT = 400;   

   private JLabel label;
   private static Logger logger = Logger.getLogger("com.horstmann.corejava");

   public ImageViewerFrame()
   {
      logger.entering("ImageViewerFrame", "<init>");      
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      // set up menu bar
      JMenuBar menuBar = new JMenuBar();
      setJMenuBar(menuBar);

      JMenu menu = new JMenu("File");
      menuBar.add(menu);

      JMenuItem openItem = new JMenuItem("Open");
      menu.add(openItem);
      openItem.addActionListener(new FileOpenListener());

      JMenuItem exitItem = new JMenuItem("Exit");
      menu.add(exitItem);
      exitItem.addActionListener(new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               logger.fine("Exiting.");
               System.exit(0);
            }
         });

      // use a label to display the images
      label = new JLabel();
      add(label);
      logger.exiting("ImageViewerFrame", "<init>");
   }

   private class FileOpenListener implements ActionListener
   {
      public void actionPerformed(ActionEvent event)
      {
         logger.entering("ImageViewerFrame.FileOpenListener", "actionPerformed", event);

         // set up file chooser
         JFileChooser chooser = new JFileChooser();
         chooser.setCurrentDirectory(new File("."));

         // accept all files ending with .gif
         chooser.setFileFilter(new javax.swing.filechooser.FileFilter()
            {
               public boolean accept(File f)
               {
                  return f.getName().toLowerCase().endsWith(".gif") || f.isDirectory();
               }

               public String getDescription()
               {
                  return "GIF Images";
               }
            });

         // show file chooser dialog
         int r = chooser.showOpenDialog(ImageViewerFrame.this);

         // if image file accepted, set it as icon of the label
         if (r == JFileChooser.APPROVE_OPTION)
         {
            String name = chooser.getSelectedFile().getPath();
            logger.log(Level.FINE, "Reading file {0}", name);
            label.setIcon(new ImageIcon(name));
         }
         else logger.fine("File open dialog canceled.");
         logger.exiting("ImageViewerFrame.FileOpenListener", "actionPerformed");
      }
   }
}

/**
 * A handler for displaying log records in a window.
 */
class WindowHandler extends StreamHandler
{
   private JFrame frame;

   public WindowHandler()
   {
      frame = new JFrame();
      final JTextArea output = new JTextArea();
      output.setEditable(false);
      frame.setSize(200, 200);
      frame.add(new JScrollPane(output));
      frame.setFocusableWindowState(false);
      frame.setVisible(true);
      setOutputStream(new OutputStream()
         {
            public void write(int b)
            {
            } // not called

            public void write(byte[] b, int off, int len)
            {
               output.append(new String(b, off, len));
            }
         });
   }

   public void publish(LogRecord record)
   {
      if (!frame.isVisible()) return;
      super.publish(record);
      flush();
   }
}