201771010106东文财《面向对象程序设计(java)》 实验8
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实验六 接口的定义与使用
实验时间 2018-10-18
一、理论知识部分
抽象类:
用abstract来声明,没有具体实例对象的类,不能用new来创建对象。可包含常规类所包含的任何东西。抽象类必须由子类继承,如果abstract类的子类不是抽象类,那么子类必须重写父类中所有的abstract方法。
接口:
用interface声明,是抽象方法和常量值定义的集合。从本质上讲,接口是一种特殊的抽象类,这种抽象类中只包含常量和方法的定义,而没有变量和方法的定义。接口中只能定义抽象方法,而且这些方法默认为是public的。只要类实现了接口,就可以在任何需要该接 口的地方使用这个类的对象。此外,一个类可以实现多个接口。
接口与抽象类的区别:
(1)接口不能实现任何方法,而抽象类可以。
(2)类可以实现许多接口,但只有一个父类。
(3)接口不是类分级结构的一部分,无任何联系的类可以实现相同的接口。
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。当拷贝一个对象变量时,原始变量与拷贝变量引用同一个对象。这样,改变一个变量所引用 的对象会对另一个变量产生影响。如果要创建一个对象新的copy,它的最初状态与 original一样,但以后可以各自改变状态,就需要使用Object类的clone方法。Object类的clone()方法是一个native方法。Object类中的clone()方法被protected修饰符修饰。这意味着在用户编写的代码中不能直接调用它。如果要直接应用clone()方法,就需覆盖clone()方法,并要把clone()方法的属性设置为public。 Object.clone()方法返回一个Object对象。必须进行强制类型转换才能得到需要的类型。
浅层拷贝:
被拷贝对象的所有常量成员和基本类型属性都有与原来对象相同的拷贝值,而若成员域是一个对象,则被拷贝对象该对象域的对象引用仍然指向原来的对象。
深层拷贝:
被拷贝对象的所有成员域都含有与原来对象相同的值,且对象域将指向被复制过的新对象,而不是原有对象被引用的对象。换言之, 深层拷贝将拷贝对象内引用的对象也拷贝一遍 。
Java中对象克隆的实现:
在子类中实现Cloneable接口。为了获取对象的一份拷贝,可以利用Object类的clone方法。在子类中覆盖超类的clone方法,声明为public。在子类的clone方法中,调用super.clone()。
二、实验部分
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。
package interfaces; public class Employee implements Comparable<Employee> { 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); } }
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); // print out information about all Employee objects for (Employee e : staff) System.out.println("name=" + e.getName() + ",salary=" + e.getSalary()); } }
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); } } |
package gh; public class yy { // TODO Auto-generated method stub 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;
package timer; /** @version 1.01 2015-05-12 @author Cay Horstmann */ import java.awt.*; import java.awt.event.*; import java.util.*; import javax.swing.*; import javax.swing.Timer; // to resolve conflict with java.util.Timer public class TimerTest { public static void main(String[] args) { ActionListener listener = new TimePrinter(); // construct a timer that calls the listener // once every 10 seconds Timer t = new Timer(10000, listener); t.start(); JOptionPane.showMessageDialog(null, "Quit program?"); System.exit(0); } } class TimePrinter implements ActionListener { public void actionPerformed(ActionEvent event) { System.out.println("At the tone, the time is " + new Date()); Toolkit.getDefaultToolkit().beep(); } }
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。
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); original.setHireDay(2000, 1, 1); Employee copy = original.clone(); copy.raiseSalary(10); copy.setHireDay(2002, 12, 31); System.out.println("original=" + original); System.out.println("copy=" + copy); } catch (CloneNotSupportedException e) { e.printStackTrace(); } } }
package clone; import java.util.Date; import java.util.GregorianCalendar; public class Employee implements Cloneable { private String name; private double salary; private Date hireDay; public Employee(String name, double salary) { this.name = name; this.salary = salary; hireDay = new Date(); } public Employee clone() throws CloneNotSupportedException { // call Object.clone() Employee cloned = (Employee) super.clone(); // 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(); // Example of instance field mutation hireDay.setTime(newHireDay.getTime()); } public void raiseSalary(double byPercent) { double raise = salary * byPercent / 100; salary += raise; } public String toString() { return "Employee[name=" + name + ",salary=" + salary + ",hireDay=" + hireDay + "]"; } }
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。
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" }; System.out.println(Arrays.toString(planets)); System.out.println("Sorted in dictionary order:"); Arrays.sort(planets); System.out.println(Arrays.toString(planets)); System.out.println("Sorted by length:"); Arrays.sort(planets, (first, second) -> first.length() - second.length()); System.out.println(Arrays.toString(planets)); Timer t = new Timer(1000, event -> System.out.println("The time is " + new Date())); t.start(); // keep program running until user selects "Ok" JOptionPane.showMessageDialog(null, "Quit program?"); System.exit(0); } }
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。
package yu; 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 yy{ private static ArrayList<People> Peoplelist; public static void main(String[] args) { Peoplelist = new ArrayList<>(); Scanner scanner = new Scanner(System.in); File file = new File("D:\\\\java\\\\1\\\\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 ID = linescanner.next(); String sex = linescanner.next(); String age = linescanner.next(); String place =linescanner.nextLine(); People People = new people(); People.setname(name); People.setID(ID); People.setsex(sex); int a = Integer.parseInt(age); People.setage(a); People.setbirthplace(place); Peoplelist.add(People); } } catch (FileNotFoundException e) { System.out.println("查找不到信息"); e.printStackTrace(); } catch (IOException e) { System.out.println("信息读取有误"); e.printStackTrace(); } boolean isTrue = true; while (isTrue) { System.out.println("————————————————————————————————————————"); System.out.println("1:按姓名字典序输出人员信息"); System.out.println("2:查询最大年龄人员信息和最小年龄人员信息"); System.out.println("3:输入你的年龄,查询年龄与你最近人的所有信息"); System.out.println("4:查询人员中是否有你的同乡"); int nextInt = scanner.nextInt(); switch (nextInt) { case 1: Collections.sort( Peoplelist); System.out.println( Peoplelist.toString()); break; case 2: int max=0,min=100;int j,k1 = 0,k2=0; for(int i=1;i< Peoplelist.size();i++) { j= Peoplelist.get(i).getage(); if(j>max) { max=j; k1=i; } if(j<min) { min=j; k2=i; } } System.out.println("年龄最大:"+ Peoplelist.get(k1)); System.out.println("年龄最小:"+ Peoplelist.get(k2)); break; case 3: System.out.println("place?"); String find = scanner.next(); String place=find.substring(0,3); String place2=find.substring(0,3); for (int i = 0; i < Peoplelist.size(); i++) { if( Peoplelist.get(i).getbirthplace().substring(1,4).equals(place)) System.out.println(Peoplelist.get(i)); } break; case 4: System.out.println("年龄:"); int yourage = scanner.nextInt(); int near=agenear(yourage); int d_value=yourage-Peoplelist.get(near).getage(); System.out.println(""+Peoplelist.get(near)); /* for (int i = 0; i < Peoplelist.size(); i++) { int p=Personlist.get(i).getage()-yourage; if(p<0) p=-p; if(p==d_value) System.out.println(Peoplelist.get(i)); } */ break; case 5: 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 min=25,d_value=0,k=0; for (int i = 0; i < Peoplelist.size(); i++) { d_value= Peoplelist.get(i).getage()-age; if(d_value<0) d_value=-d_value; if (d_value<min) { min=d_value; k=i; } } return k; } }
package yu; public class yu { public abstract class People implements Comparable<People> { private String name; private String ID; private int age; private String sex; private String birthplace; public String getname() { return name; } public void setname(String name) { this.name = name; } public String getID() { return ID; } public void setID(String ID) { this.ID= ID; } public int getage() { return age; } public void setage(int age) { // int a = Integer.parseInt(age); this.age= age; } public String getsex() { return sex; } public void setsex(String sex) { this.sex= sex; } public String getbirthplace() { return birthplace; } public void setbirthplace(String birthplace) { this.birthplace= birthplace; } public int compareTo(People o) { return this.name.compareTo(o.getname()); } public String toString() { return name+"\\t"+sex+"\\t"+age+"\\t"+ID+"\\t"+birthplace+"\\n"; } } }
实验结果:
实验4:内部类语法验证实验
实验程序1:
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。
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(); // 在按确定之前,程序一直运行 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();//构造器 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。
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();//TalkingClock类声明为私有的 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(); //外围类引用. } }; 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。
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:
通过这章的学习我了解了接口的使用和他的功能,学会了Lambda表达式与内部类。也学会了建立浅拷贝与深拷贝,总的来说本章的知识点还是挺多的。以后我会继续努力,争取敲更多好的代码。
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