201771010106东文财《面向对象程序设计（java）》实验9

实验九 异常、断言与日志

实验时间 2018-10-25

1、实验目的与要求

(1) 掌握java异常处理技术；

(2) 了解断言的用法；

(3) 了解日志的用途；

(4) 掌握程序基础调试技巧；

2、实验内容和步骤

实验1：用命令行与IDE两种环境下编辑调试运行源程序ExceptionDemo1、ExceptionDemo2，结合程序运行结果理解程序，掌握未检查异常和已检查异常的区别。

//异常示例1

public class ExceptionDemo1 {

public static void main(String args[]) {

int a = 0;

System.out.println(5 / a);

}

}

//异常示例2

import java.io.*;

public class ExceptionDemo2 {

public static void main(String args[])

     {

          FileInputStream fis=new FileInputStream("text.txt");//JVM自动生成异常对象

          int b;

          while((b=fis.read())!=-1)

          {

              System.out.print(b);

          }

          fis.close();

      }

}

package tt;
public class ExceptionDemo1 {

public static void main(String args[]) {

int a = 0;

System.out.println(5 / a);

}

}

package tt;
import java.io.*;



public class ExceptionDemo2 {

public static void main(String args[])

     {

          FileInputStream fis = null;
        try {
            fis = new FileInputStream("C:\\Users\\LENOVO\\Desktop\\text.txt");
        } catch (FileNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }//JVM自动生成异常对象

          int b;

          try {
            while((b=fis.read())!=-1)

              {

                  System.out.print(b);

              }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

          try {
            fis.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

      }

  
}

实验结果：

实验2： 导入以下示例程序，测试程序并进行代码注释。

测试程序1：

l 在elipse IDE中编辑、编译、调试运行教材281页7-1，结合程序运行结果理解程序；

l 在程序中相关代码处添加新知识的注释；

l 掌握Throwable类的堆栈跟踪方法；

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();//构造一个Throwable 对象
      StackTraceElement[] frames = t.getStackTrace();//获得构造这个对象时调用的对战的跟踪
      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);
   }
}

实验结果：

测试程序2：

l Java语言的异常处理有积极处理方法和消极处理两种方式；

l 下列两个简答程序范例给出了两种异常处理的代码格式。在elipse IDE中编辑、调试运行源程序ExceptionalTest.java，将程序中的text文件更换为身份证号.txt，要求将文件内容读入内容，并在控制台显示；

l 掌握两种异常处理技术的特点。

//积极处理方式　　

import java.io.*;

class ExceptionTest {

public static void main (string args[])

   {

       try{

       FileInputStream fis=new FileInputStream("text.txt");

       }

       catch（FileNotFoundExcption e）

     {   ……  }

……

    }

}

//消极处理方式

import java.io.*;

class ExceptionTest {

public static void main (string args[]) throws  FileNotFoundExcption

     {

      FileInputStream fis=new FileInputStream("text.txt");

     }

}

package tt;

//积极处理方式　　
import java.io.*;
import java.io.BufferedReader;
import java.io.FileReader;

class ExceptionTest {
    public static void main (String args[])
 {
        File fis=new File("C:\\\\Users\\\\LENOVO\\\\Desktop\\\\身份证号.txt");
     try{
         

         FileReader fr = new FileReader(fis);
         BufferedReader br = new BufferedReader(fr);
         try {
             String s, s2 = new String();
             while ((s = br.readLine()) != null) {
                 s2 += s + "\n ";
             }
             br.close();
             System.out.println(s2);
         } catch (IOException e) {
             // TODO Auto-generated catch block
             e.printStackTrace();
         }
     } catch (FileNotFoundException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
     }

  }
}

package tt;

//消极处理方式

import java.io.*;
class ExceptionDemo2 {
    public static void main (String args[]) throws  IOException
       {
        File fis=new File("C:\\Users\\LENOVO\\Desktop\\身份证号.txt");
        FileReader fr = new FileReader(fis);
        BufferedReader br = new BufferedReader(fr);
        String s, s2 = new String();

            while ((s = br.readLine()) != null) {
                s2 += s + "\n ";
            }
            br.close();
            System.out.println(s2);
       }
}

实验结果：

实验3: 编程练习

练习1：

l 编制一个程序，将身份证号.txt 中的信息读入到内存中；

l 按姓名字典序输出人员信息；

l 查询最大年龄的人员信息；

l 查询最小年龄人员信息；

l 输入你的年龄，查询身份证号.txt中年龄与你最近人的姓名、身份证号、年龄、性别和出生地；

l 查询人员中是否有你的同乡；

l 在以上程序适当位置加入异常捕获代码。

注：以下实验课后完成

package gh;



    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.util.ArrayList;
    import java.util.Scanner;
    import java.util.Collections;

    public class tt {

        public static People findPeopleByname(String name) {
            People flag = null;
            for (People people : peoplelist) {
                if(people.getName().equals(name)) {
                    flag = people;
                }
            }
            return flag;

        }

        public static People findPeopleByid(String id) {
            People flag = null;
            for (People people : peoplelist) {
                if(people.getnumber().equals(id)) {
                    flag = people;
                }
            }
            return flag;

        }
         
        private static ArrayList<People> agenear(int yourage) {
            // TODO Auto-generated method stub
            int j=0,min=53,d_value=0,k = 0;
            ArrayList<People> plist = new ArrayList<People>();
            for (int i = 0; i < peoplelist.size(); i++) {
                d_value = peoplelist.get(i).getage() > yourage ? 
                        peoplelist.get(i).getage() - yourage : yourage - peoplelist.get(i).getage() ;
                k = d_value < min ? i : k;
                min = d_value < min ? d_value : min;
            }
            for(People people : peoplelist) {
                if(people.getage() == peoplelist.get(k).getage()) {
                    plist.add(people);
                }
            }
            return plist;
        }

        private static ArrayList<People> peoplelist; 
        
        public static void main(String[] args) //throws  IOException
        {
            peoplelist = new ArrayList<People>();
            Scanner scanner = new Scanner(System.in);
            File file = new File("D:\\身份证号.txt");
            try {
                FileInputStream files = new FileInputStream(file);
                BufferedReader in = new BufferedReader(new InputStreamReader(files));
                String temp = null;
                while ((temp = in.readLine()) != null) {
                    
                    String[] information = temp.split("[ ]+");
                    People people = new People();
                    people.setName(information[0]);
                    people.setnumber(information[1]);
                    int A = Integer.parseInt(information[3]);
                    people.setage(A);
                    people.setsex(information[2]);
                    for(int j = 4; j<information.length;j++) {
                        people.setplace(information[j]);
                    }
                    peoplelist.add(people);

                }
            } catch (FileNotFoundException e) {
                System.out.println("文件未找到");
                e.printStackTrace();
            } catch (IOException e) {
                System.out.println("文件读取错误");
                e.printStackTrace();
            }
            boolean isTrue = true;
            while (isTrue) {

                System.out.println("******************************************");
                System.out.println("   1.按姓名典序输出人员信息");
                System.out.println("   2.查询最大年龄人员信息");
                System.out.println("   3.查询最小年龄人员信息");
                System.out.println("   4.输入你的年龄，查询身份证号.txt中年龄与你最近的人");
                System.out.println("   5.查询人员中是否有你的同乡");
                System.out.println("   6.退出");
                System.out.println("******************************************");
                int nextInt = scanner.nextInt();
                switch (nextInt) {
                case 1:
                    Collections.sort(peoplelist);
                    System.out.println(peoplelist.toString());
                    break;
                case 2:
                    int max=0;
                    int j,k1 = 0;
                    for(int i=1;i<peoplelist.size();i++)
                    {
                        j = peoplelist.get(i).getage();
                       if(j>max)
                       {
                           max = j; 
                           k1 = i;
                       }
                      
                    }  
                    System.out.println("年龄最大："+peoplelist.get(k1));
                    break;
                case 3:
                    int min = 100;
                    int j1,k2 = 0;
                    for(int i=1;i<peoplelist.size();i++)
                    {
                        j1 = peoplelist.get(i).getage();
                        if(j1<min)
                        {
                            min = j1; 
                            k2 = i;
                        }

                     } 
                    System.out.println("年龄最小："+peoplelist.get(k2));
                    break;
                case 4:
                    System.out.println("年龄：");
                    int input_age = scanner.nextInt();
                    ArrayList<People> plist = new ArrayList<People>();
                    plist = agenear(input_age);
                    for(People people : plist) {
                        System.out.println(people.toString());
                    }
                    break;
                case 5:
                    System.out.println("请输入省份");
                    String find = scanner.next();        
                    for (int i = 0; i <peoplelist.size(); i++) 
                    {
                        String [] place = peoplelist.get(i).getplace().split("\t");
                        for(String temp : place) {
                            if(find.equals(temp)) {
                                System.out.println("你的同乡是    "+peoplelist.get(i));
                                break;
                            }
                        }
                        
                    } 
                    break;
                case 6:
                    isTrue = false;
                    System.out.println("byebye!");
                    break;
                default:
                    System.out.println("输入有误");
                }
            }
        }

    }
}

实验结果：

练习2：

l 编写一个计算器类，可以完成加、减、乘、除的操作；

l 利用计算机类，设计一个小学生100以内数的四则运算练习程序，由计算机随机产生10道加减乘除练习题，学生输入答案，由程序检查答案是否正确，每道题正确计10分，错误不计分，10道题测试结束后给出测试总分；

l 将程序中测试练习题及学生答题结果输出到文件，文件名为test.txt；

l 在以上程序适当位置加入异常捕获代码。

package rt;


    import java.io.FileNotFoundException;
    import java.io.PrintWriter;
    import java.util.Scanner;
    public class tt {
        public static void main(String[] args) {
            Scanner in = new Scanner(System.in);
            tt1 computing=new tt1();
            PrintWriter output = null;
            try {
                output = new PrintWriter("tt.txt");
            } catch (Exception e) {
            }
            int sum = 0;

            for (int i = 1; i < 11; i++) {
                int a = (int) Math.round(Math.random() * 100);
                int b = (int) Math.round(Math.random() * 100);
                int s = (int) Math.round(Math.random() * 3);
            switch(s)
            {
               case 1:
                   System.out.println(i+": "+a+"/"+b+"=");
                   while(b==0){  
                       b = (int) Math.round(Math.random() * 100); 
                       }
                   double c = in.nextDouble();
                   output.println(a+"/"+b+"="+c);
                   if (c == (double)computing.division(a, b)) {
                       sum += 10;
                       System.out.println("正确");
                   }
                   else {
                       System.out.println("错误");
                   }
                
                   break;
                
               case 2:
                   System.out.println(i+": "+a+"*"+b+"=");
                   int c1 = in.nextInt();
                   output.println(a+"*"+b+"="+c1);
                   if (c1 == computing.multiplication(a, b)) {
                       sum += 10;
                       System.out.println("正确");
                   }
                   else {
                       System.out.println("错误");
                   }
                   break;
               case 3:
                   System.out.println(i+": "+a+"+"+b+"=");
                   int c2 = in.nextInt();
                   output.println(a+"+"+b+"="+c2);
                   if (c2 == computing.addition(a, b)) {
                       sum += 10;
                       System.out.println("正确");
                   }
                   else {
                       System.out.println("错误");
                   }
                   
                   break ;
               case 4:
                   System.out.println(i+": "+a+"-"+b+"=");
                   int c3 = in.nextInt();
                   output.println(a+"-"+b+"="+c3);
                   if (c3 == computing.subtraction(a, b)) {
                       sum += 10;
                       System.out.println("正确");
                   }
                   else {
                       System.out.println("错误");
                   }
                   break ;

                   } 
        
              }
            System.out.println("成绩："+sum+"分");
            output.println("成绩："+sum+"分");
            output.close();
             
        }
    }
    class tt1
    {
           private int a;
           private int b;
            public int  addition(int a,int b)
            {
                return a+b;
            }
            public int  subtraction(int a,int b)
            {
                if((a-b)<0)
                    return 0;
                else
                return a-b;
            }
            public int   multiplication(int a,int b)
            {
                return a*b;
            }
            public int   division(int a,int b)
            {
                if(b!=0)
                return a/b;    
                else
            return 0;
            }

            
    }

实验结果：

 

实验4：断言、日志、程序调试技巧验证实验。

实验程序1：

//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);

    }

}

l 在elipse下调试程序AssertDemo，结合程序运行结果理解程序；

l 注释语句test1(-5);后重新运行程序，结合程序运行结果理解程序；

l 掌握断言的使用特点及用法。

package rt;

public class tt {



        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);

        }

    }

 实验结果：

实验程序2：

l 用JDK命令调试运行教材298页-300页程序7-2，结合程序运行结果理解程序；

l 并掌握Java日志系统的用途及用法。

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();
   }
}

实验结果：

实验程序3：

l 用JDK命令调试运行教材298页-300页程序7-2，结合程序运行结果理解程序；

l 按课件66-77内容练习并掌握Elipse的常用调试技术。

实验总结：

      本次实验我的收获还是挺大的，通过一些示例程序的的编译、运行，我对本章的知识有了一定的了解，知道了对于程序中的一些错误的改正方法，也知道了断言的用法和日志的用途。不过本章中依然有一些知识点不是很了解，在今后的学习中我会继续加油，争取搞懂这些不懂的知识点。多多敲代码，希望以后我的编程技术会有很大的进步。