张季跃 201771010139《面向对象程序设计（java）》第八周学习总结

Posted 2021-01-14 alex-morcer

张季跃 201771010139《面向对象程序设计（java）》第八周学习总结

理论知识部分：

6.1 接口

l(1)Java为了克服单继承的缺点，Java使用了接口， 一个类可以实现一个或多个接口。 l

(2) 在Java程序设计语言中，接口不是类，而是对类 的一组需求描述，由常量和一组抽象方法组成。 l

(3) 接口中不包括变量和有具体实现的方法。 l

(4) 只要类实现了接口，则该类要遵从接口描述的统 一格式进行定义，并且可以在任何需要该接口的 地方使用这个类的对象.

6.2 接口示例

l(1)接口与回调

la.回调(callback)：一种程序设计模式，在这种模 式中，可指出某个特定事件发生时程序应该采取 的动作。 l

B.在java.swing包中有一个Timer类，可以使用它 在到达给定的时间间隔时触发一个事件。

l(2)Comparator接口

la.所在包：java.util.* l

b.Comparator接口定义

lc.用途一：处理字符串按长度进行排序的操作
(3)对象克隆

la.Object类的Clone方法

lb.浅层拷贝与深层拷贝

lc.Java中对象克隆的实现

6.3 lambda表达式

lJava Lambda 表达式是Java 8 引入的一个新的功能，主 要用途是提供一个函数化的语法来简化编码

1、实验目的与要求

(1) 掌握接口定义方法；

(2) 掌握实现接口类的定义要求；

(3) 掌握实现了接口类的使用要求；

(4) 掌握程序回调设计模式；

(5) 掌握Comparator接口用法；

(6) 掌握对象浅层拷贝与深层拷贝方法；

(7) 掌握Lambda表达式语法；

(8) 了解内部类的用途及语法要求。

2、实验内容和步骤

实验1： 导入第6章示例程序，测试程序并进行代码注释。

测试程序1：

l 编辑、编译、调试运行阅读教材214页-215页程序6-1、6-2，理解程序并分析程序运行结果；

l 在程序中相关代码处添加新知识的注释。

l 掌握接口的实现用法；

l 掌握内置接口Compareable的用法。

实验代码：

package interfaces;

 

import java.util.*;

 

/**

 * This program demonstrates the use of the Comparable interface.

 * @version 1.30 2004-02-27

 * @author Cay Horstmann

 */

public class EmployeeSortTest

{

   public static void main(String[] args)

   {

      Employee[] staff = new Employee[3];

 

      staff[0] = new Employee("Harry Hacker", 35000);

      staff[1] = new Employee("Carl Cracker", 75000);

      staff[2] = new Employee("Tony Tester", 38000);

 

      Arrays.sort(staff);

 

      //输出所有关于Employee对象的信息

      for (Employee e : staff)

         System.out.println("name=" + e.getName() + ",salary=" + e.getSalary());

   }

}

 

package interfaces;

 

public class Employee implements Comparable<Employee>

//创建一个泛型Comparable接口，提供一个类型参数，比较Employee类的对象并进行排序

{

   private String name;

   private double salary;

 

   public Employee(String name, double salary)

   {

      this.name = name;

      this.salary = salary;

   }

 

   public String getName()

   {

      return name;

   }

 

   public double getSalary()

   {

      return salary;

   }

 

   public void raiseSalary(double byPercent)

   {

      double raise = salary * byPercent / 100;

      salary += raise;

   }

 

   /**

    * Compares employees by salary

    * @param other another Employee object

    * @return a negative value if this employee has a lower salary than

    * otherObject, 0 if the salaries are the same, a positive value otherwise

    */

   public int compareTo(Employee other)

   {

      return Double.compare(salary, other.salary);

    //salary的大小两两互相比较，升序排出salary的大小

   }

}

实验结果：

 

 

测试程序2：

l 编辑、编译、调试以下程序，结合程序运行结果理解程序；

interface  A {   double g=9.8;   void show( ); } class C implements A {   public void show( )   {System.out.println("g="+g);} }   class InterfaceTest {   public static void main(String[ ] args)   {        A a=new C( );        a.show( );        System.out.println("g="+C.g);   } }

实验结果：

 

 

 

测试程序3：

l 在elipse IDE中调试运行教材223页6-3，结合程序运行结果理解程序；

l 26行、36行代码参阅224页，详细内容涉及教材12章。

l 在程序中相关代码处添加新知识的注释。

l 掌握回调程序设计模式；

实验程序：

interface  A

{

  double g=9.8;

  void show( );

}

class C implements A

{

  public void show( )

  {System.out.println("g="+g);}

}

 

class InterfaceTest

{

  public static void main(String[ ] args)

  {

       A a=new C( );

       a.show( );

       System.out.println("g="+C.g);

  }

}

实验结果：

 

 

测试程序4：

l 调试运行教材229页-231页程序6-4、6-5，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 掌握对象克隆实现技术；

l 掌握浅拷贝和深拷贝的差别。

实验程序：

package clone;

 

/**

 * This program demonstrates cloning.

 * @version 1.10 2002-07-01

 * @author Cay Horstmann

 */

public class CloneTest

{

   public static void main(String[] args)

   {

      try

      {

        

         Employee original = new Employee("John Q. Public", 50000);

         //Employee是一个自定义类

         original.setHireDay(2000, 1, 1);

         Employee copy = original.clone();

         copy.raiseSalary(10);//原有对象不会发生变化

         copy.setHireDay(2002, 12, 31);//更改器

         System.out.println("original=" + original);//字符串连接

         System.out.println("copy=" + copy);

      }

      catch (CloneNotSupportedException e)

      {

         e.printStackTrace();

      }

   }

}

实验结果：

 

 

实验2： 导入第6章示例程序6-6，学习Lambda表达式用法。

l 调试运行教材233页-234页程序6-6，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 将27-29行代码与教材223页程序对比，将27-29行代码与此程序对比，体会Lambda表达式的优点。

实验程序：

package lambda;

 

import java.util.*;

 

import javax.swing.*;

import javax.swing.Timer;

 

/**

 * This program demonstrates the use of lambda expressions.

 * @version 1.0 2015-05-12

 * @author Cay Horstmann

 */

public class LambdaTest

{

   public static void main(String[] args)

   {

      String[] planets = new String[] { "Mercury", "Venus", "Earth", "Mars",

            "Jupiter", "Saturn", "Uranus", "Neptune" };//定义数组planets

      System.out.println(Arrays.toString(planets));//静态方法

      System.out.println("Sorted in dictionary order:");

      Arrays.sort(planets);//Arrays.sort方法接收实验Lambda类的对象

      System.out.println(Arrays.toString(planets));

      System.out.println("Sorted by length:");

      Arrays.sort(planets, (first, second) -> first.length() - second.length());//Lambda表达式

      System.out.println(Arrays.toString(planets));

            

      Timer t = new Timer(1000, event ->

         System.out.println("The time is " + new Date()));//Lambda表达式

      t.start();   

         

      // keep program running until user selects "Ok"

      JOptionPane.showMessageDialog(null, "Quit program?");

      System.exit(0);   //返回类型      

   }

}

 

package clone;

 

import java.util.Date;

import java.util.GregorianCalendar;

 

public class Employee implements Cloneable

{

//定义三个私有属性

   private String name;//string类在lang包

   private double salary;

   private Date hireDay;

 

   public Employee(String name, double salary)

   {

      this.name = name;

      this.salary = salary;

      hireDay = new Date();

   }//构造方法

 

   public Employee clone() throws CloneNotSupportedException

   {

      // call Object.clone()

      Employee cloned = (Employee) super.clone();//强制类型转换

 

      // clone mutable fields

      cloned.hireDay = (Date) hireDay.clone();

 

      return cloned;

   }

 

   /**

    * Set the hire day to a given date.

    * @param year the year of the hire day

    * @param month the month of the hire day

    * @param day the day of the hire day

    */

   public void setHireDay(int year, int month, int day)

   {

      Date newHireDay = new GregorianCalendar(year, month - 1, day).getTime();

       //创建一个实例字段变异的实例

      // Example of instance field mutation

      hireDay.setTime(newHireDay.getTime());

   }

 

   public void raiseSalary(double byPercent)

   {

      double raise = salary * byPercent / 100;

      salary += raise;

   }//调用

 

   public String toString()

   {

      return "Employee[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay + "]";

   }

}

实验结果：

 

 

注：以下实验课后完成

实验3: 编程练习

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。

实验程序：

package shen;

 

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.Arrays;

import java.util.Collections;

import java.util.Scanner;

 

public class Main{

    private static ArrayList<Student> studentlist;

    public static void main(String[] args) {

        studentlist = new ArrayList<>();

        Scanner scanner = new Scanner(System.in);

        File file = new File("C:\\Users\\ASUS\\Desktop\\新建文件夹\\身份证号.txt");

        try {

            FileInputStream fis = new FileInputStream(file);

            BufferedReader in = new BufferedReader(new InputStreamReader(fis));

            String temp = null;

            while ((temp = in.readLine()) != null) {

                

                Scanner linescanner = new Scanner(temp);

                

                linescanner.useDelimiter(" ");    

                String name = linescanner.next();

                String number = linescanner.next();

                String sex = linescanner.next();

                String age = linescanner.next();

                String province =linescanner.nextLine();

                Student student = new Student();

                student.setName(name);

                student.setnumber(number);

                student.setsex(sex);

                int a = Integer.parseInt(age);

                student.setage(a);

                student.setprovince(province);

                studentlist.add(student);

 

            }

        } catch (FileNotFoundException e) {

            System.out.println("学生信息文件找不到");

            e.printStackTrace();

        } catch (IOException e) {

            System.out.println("学生信息文件读取错误");

            e.printStackTrace();

        }

        boolean isTrue = true;

        while (isTrue) {

            System.out.println("选择你的操作，输入正确格式的选项");

            System.out.println("A.字典排序");

            System.out.println("B.输出年龄最大和年龄最小的人");

            System.out.println("C.寻找老乡");

            System.out.println("D.寻找年龄相近的人");

            System.out.println("F.退出");

            String m = scanner.next();

            switch (m) {

            case "A":

                Collections.sort(studentlist);              

                System.out.println(studentlist.toString());

                break;

            case "B":

                 int max=0,min=100;

                 int j,k1 = 0,k2=0;

                 for(int i=1;i<studentlist.size();i++)

                 {

                     j=studentlist.get(i).getage();

                 if(j>max)

                 {

                     max=j;

                     k1=i;

                 }

                 if(j<min)

                 {

                   min=j;

                   k2=i;

                 }

                 

                 }  

                 System.out.println("年龄最大："+studentlist.get(k1));

                 System.out.println("年龄最小："+studentlist.get(k2));

                break;

            case "C":

                 System.out.println("老家?");

                 String find = scanner.next();        

                 String place=find.substring(0,3);

                 for (int i = 0; i <studentlist.size(); i++)

                 {

                     if(studentlist.get(i).getprovince().substring(1,4).equals(place))

                         System.out.println("老乡"+studentlist.get(i));

                 }             

                 break;

                 

            case "D":

                System.out.println("年龄：");

                int yourage = scanner.nextInt();

                int near=agenear(yourage);

                int value=yourage-studentlist.get(near).getage();

                System.out.println(""+studentlist.get(near));

                break;

            case "F":

                isTrue = false;

                System.out.println("退出程序!");

                break;

                default:

                System.out.println("输入有误");

 

            }

        }

    }

        public static int agenear(int age) {      

        int j=0,min=53,value=0,k=0;

         for (int i = 0; i < studentlist.size(); i++)

         {

             value=studentlist.get(i).getage()-age;

             if(value<0) value=-value;

             if (value<min)

             {

                min=value;

                k=i;

             }

          }    

         return k;         

      }

 

}

 

Main

 

package shen;

 

public class Student implements Comparable<Student> {

 

    private String name;

    private String number ;

    private String sex ;

    private int age;

    private String province;

   

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public String getnumber() {

        return number;

    }

    public void setnumber(String number) {

        this.number = number;

    }

    public String getsex() {

        return sex ;

    }

    public void setsex(String sex ) {

        this.sex =sex ;

    }

    public int getage() {

 

        return age;

        }

        public void setage(int age) {

            // int a = Integer.parseInt(age);

        this.age= age;

        }

 

    public String getprovince() {

        return province;

    }

    public void setprovince(String province) {

        this.province=province ;

    }

 

    public int compareTo(Student o) {

       return this.name.compareTo(o.getName());

    }

 

    public String toString() {

        return  name+" "+sex+" "+age+" "+number+" "+province+" ";

    }    

}

实验结果

 

 

 

l 编辑、调试运行教材246页-247页程序6-7，结合程序运行结果理解程序；

l 了解内部类的基本用法。

实验程序：

package innerClass;

 

import java.awt.*;

import java.awt.event.*;

import java.util.*;

import javax.swing.*;

import javax.swing.Timer;

 

/**

 * This program demonstrates the use of inner classes.

 * @version 1.11 2015-05-12

 * @author Cay Horstmann

 */

public class InnerClassTest

{

   public static void main(String[] args)

   {

      TalkingClock clock = new TalkingClock(1000, true);

      clock.start();

 

      // keep program running until user selects "Ok"

      JOptionPane.showMessageDialog(null, "Quit program?");

      System.exit(0);

   }

}

 

/**

 * A clock that prints the time in regular intervals.

 */

class TalkingClock

{

   private int interval;

   private boolean beep;

 

   /**

    * Constructs a talking clock

    * @param interval the interval between messages (in milliseconds)

    * @param beep true if the clock should beep

    */

   public TalkingClock(int interval, boolean beep)

   {

      this.interval = interval;

      this.beep = beep;

   }

 

   /**

    * Starts the clock.

    */

   public void start()

   {

      ActionListener listener = new TimePrinter();

      Timer t = new Timer(interval, listener);

      t.start();

   }

 

   public class TimePrinter implements ActionListener

   {

      public void actionPerformed(ActionEvent event)

      {

         System.out.println("At the tone, the time is " + new Date());

         if (beep) Toolkit.getDefaultToolkit().beep();

      }

   }

}

实验结果：

 

 

实验程序2：

l 编辑、调试运行教材254页程序6-8，结合程序运行结果理解程序；

l 了解匿名内部类的用法。

实验程序：

package anonymousInnerClass;

 

import java.awt.*;

import java.awt.event.*;

import java.util.*;

import javax.swing.*;

import javax.swing.Timer;

 

/**

 * This program demonstrates anonymous inner classes.

 * @version 1.11 2015-05-12

 * @author Cay Horstmann

 */

public class AnonymousInnerClassTest

{

   public static void main(String[] args)

   {

      TalkingClock clock = new TalkingClock();

      clock.start(1000, true);

 

      // keep program running until user selects "Ok"

      JOptionPane.showMessageDialog(null, "Quit program?");

      System.exit(0);

   }

}

 

/**

 * A clock that prints the time in regular intervals.

 */

class TalkingClock

{

   /**

    * Starts the clock.

    * @param interval the interval between messages (in milliseconds)

    * @param beep true if the clock should beep

    */

   public void start(int interval, boolean beep)

   {

      ActionListener listener = new ActionListener()

         {

            public void actionPerformed(ActionEvent event)

            {

               System.out.println("At the tone, the time is " + new Date());

               if (beep) Toolkit.getDefaultToolkit().beep();

            }

         };

      Timer t = new Timer(interval, listener);

      t.start();

   }

}

实验结果：

 

 

实验程序3：

l 在elipse IDE中调试运行教材257页-258页程序6-9，结合程序运行结果理解程序；

l 了解静态内部类的用法。

实验程序：package staticInnerClass;

 

/**

 * This program demonstrates the use of static inner classes.

 * @version 1.02 2015-05-12

 * @author Cay Horstmann

 */

public class StaticInnerClassTest

{

   public static void main(String[] args)

   {

      double[] d = new double[20];

      for (int i = 0; i < d.length; i++)

         d[i] = 100 * Math.random();

      ArrayAlg.Pair p = ArrayAlg.minmax(d);

      System.out.println("min = " + p.getFirst());

      System.out.println("max = " + p.getSecond());

   }

}

 

class ArrayAlg

{

   /**

    * A pair of floating-point numbers

    */

   public static class Pair

   {

      private double first;

      private double second;

 

      /**

       * Constructs a pair from two floating-point numbers

       * @param f the first number

       * @param s the second number

       */

      public Pair(double f, double s)

      {

         first = f;

         second = s;

      }

 

      /**

       * Returns the first number of the pair

       * @return the first number

       */

      public double getFirst()

      {

         return first;

      }

 

      /**

       * Returns the second number of the pair

       * @return the second number

       */

      public double getSecond()

      {

         return second;

      }

   }

 

   /**

    * Computes both the minimum and the maximum of an array

    * @param values an array of floating-point numbers

    * @return a pair whose first element is the minimum and whose second element

    * is the maximum

    */

   public static Pair minmax(double[] values)

   {

      double min = Double.POSITIVE_INFINITY;

      double max = Double.NEGATIVE_INFINITY;

      for (double v : values)

      {

         if (min > v) min = v;

         if (max < v) max = v;

      }

      return new Pair(min, max);

   }

}

实验结果：

 

 

实验总结：

在本周的学习过程中，我第一次接触了接口的概念并对有关知识的应用有了初步的掌握。并且在学习过程中，我学习到了有关回调与对象克隆的知识。最后，我还对Lambda表达式有了初步的认识。但总体而言，我本周的学习并没有得到太大的成果，做实验报告时遇到了很多搞不懂东西，就算请教了同学也没有完全理解。