实验六 接口的定义与使用
实验时间 2018-10-18
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:
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;
在程序中相关代码处添加新知识的注释。
掌握接口的实现用法;
掌握内置接口Compareable的用法。
程序源代码:
Employee。java
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; } //name访问器 public double getSalary() { return salary; } //salary访问器 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); } }
EmployeeSortTest.java
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);//静态方法 // print out information about all Employee objects for (Employee e : staff) System.out.println("name=" + e.getName() + ",salary=" + e.getSalary()); } }
程序测试结果:
Compareable的用法:
任何实现Compareable接口的类都需要包含compareTo的方法,并且这个方法的参数必须是一个Object对象,返回一个整型数值。
测试程序2:
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); } } |
程序源代码及其新知识注释:
interface A//定义一个接口,接口名为A { double g=9.8;//定义一个g=9.8 void show( );//调用一个void方法,但这个方法为空 } 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); } }
程序测试结果:
测试程序3:
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;
26行、36行代码参阅224页,详细内容涉及教材12章。
在程序中相关代码处添加新知识的注释。
掌握回调程序设计模式;
程序源代码:
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; // 解决与java.util.Timer的冲突 public class TimerTest { public static void main(String[] args) { ActionListener listener = new TimePrinter(); // 构造一个调用侦听器的计时器 // 每10秒一次 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(); } }
程序测试结果:
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。
程序源代码:
Employee。java
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 { // 调用Object.clone() Employee cloned = (Employee) super.clone(); // 克隆可变的字段 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(); // 实例字段突变的例子 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 + "]"; } }
CloneTest.java
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(); } } }
测试结果:
实验2: 导入第6章示例程序6-6,学习Lambda表达式用法。
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;
在程序中相关代码处添加新知识的注释。
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。
程序源代码:
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); } }
程序测试结果:
注:以下实验课后完成
实验3: 编程练习
编制一个程序,将身份证号.txt 中的信息读入到内存中;
按姓名字典序输出人员信息;
查询最大年龄的人员信息;
查询最小年龄人员信息;
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;
查询人员中是否有你的同乡。
程序源代码:
Main.java:
package Test; 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("D:\\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("e.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 "e": 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; } }
Student.java:
package Test; 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+"\t"+sex+"\t"+age+"\t"+number+"\t"+province+"\n"; } }
程序测试结果:
实验4:内部类语法验证实验
实验程序1:
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;
了解内部类的基本用法。
程序源代码:
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(); // 保持程序运行,直到用户选择“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(); } } }
程序测试结果:
实验程序2:
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;
了解匿名内部类的用法。
程序源代码及其注释:
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); // 保持程序运行,直到用户选择“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(); } }
程序测试结果:
实验程序3:
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;
了解静态内部类的用法。
程序源代码:
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); } }
程序测试结果:
学习总结:
接口的定义方法: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。接口中不包括变量和有具体实现的方法。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。
接口的实现:类声明时用implements关键字声明使用一个或多个接口,一个类使用了某个接口,那么这个类必须实现,接口的所有方法,即为这些方法提供方法体。
一个类可以实现多个接口,接口间应该用逗号分隔开。
接口的使用要求:接口不能构造接口对象,但可以声明接口变量以指向一个实现了该接口的类对象。
程序回调: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。
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。
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
以上是对本周所学理论知识的一个总结,其次就是在本周的实验课上,在做实验时,有学长以及老师的讲解,是我对接口的知识有了更深一层的理解,以及在后面的自主练习的实验中,虽然对实验的认知还不太透彻,希望在后期的学习中能加强吧。