第八周实验总结
一、知识总结
接口的总结:
1.接口本身 是一个特殊的类
2.接口的成员变量 默认是 public static final 修饰的,也就是说接口中的成员变量实际上是一个常量
3.接口中的 方法 都是抽象方法,默认修饰 public abstract
4.接口是不能够创建对象的
5.接口是没有构造方法
6.因为接口是提供给 类 去使用的,非抽象类去实现一个接口的时候,必须要把接口中所有的方法 都要实现。
接口的语法:
修饰符 interface 接口类{} 或者 修饰符 interface 接口类 extends 父接口1,父接口2{}
类实现的语法:
class 类名 extends 父类名 implements 接口1,接口2{类的内容}
接口方法的定义:
1.接口中的方法都是抽象方法。
2.接口中的方法,不能有任何的修饰。
3.编译器在编译的时候会自动为你加上public static fianl修饰。
如何使用接口的例子:
//定义接口类
interface Lock{
void unlock();
}
// 创建父类链接接口
abstract class Door implements Lock{
void openDoor(){
}
}
子类继承父类,并继承父类链接的接口并重写方法
class ThelfProofDoor extends Door{
public void unlock(){
}
}
接口的作用:
1.扩展功能
2.定义约束规范
3.程序解耦合性
类和接口的注意点:
1.当一个 <非抽象类> 在实现 接口的时候,必须实现接口中 <所有的方法>
2.当一个抽象类,在实现接口的时候,可以实现也可以不实现 接口中的方法, 因为抽象类的子类来实现
3.一个类可以实现多个接口
4. 因为抽象类本身就不能够被实例化,它给子类继承用的,所以它不可以实现这个接口中的方法,而让对应的子类来实现就可以了。(注意:如果子类也没有实现接口中的方法,则会出错。)
接口与接口之间的关系:
在java中类是单继承的,一个类只有一个直接父类,接口也是可以继承的,但是它是多继承的,也就是一个接口可以继承多个接口(接口的继承是指继承接口的方法,而且能够多继承的关键点是接口的方法是实现这个接口的类来实现的)
例如:
interface A{
void test();
}
interface B{
void test2();
}
class Test implements A,B{
public void test(){
}
public void test2(){
}
}
并且类与类之间出来继承,接口,还有关联。而关联又分为依赖、聚合、组合依赖。
二、实验内容(接口的定义与使用)
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; 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); // 打印所有员工对象的信息 for (Employee e : staff) System.out.println("name=" + e.getName() + ",salary=" + e.getSalary()); } }
package interfaces; //将类声明为实现为某个接口,使用implements关键字 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) { // 这里使用了静态Double.compare方法,且为泛型Comparable提供了一个类型参数 return Double.compare(salary, other.salary); } }
package interfaces; //将类声明为实现为某个接口,使用implements关键字 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) { // 这里使用了静态Double.compare方法,且为泛型Comparable提供了一个类型参数 return Double.compare(salary, other.salary); } }
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); } } |
代码:
package g; class InterfaceTest { public static void main(String[ ] args) { A a=new C( ); a.show( ); System.out.println("g="+C.g); } }
package g; interface A { double g=9.8; void show( ); }
package g; class C implements A { public void show( ) {System.out.println("g="+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(); // 构造一个timer对象存放在变量里,叫做listener // 每次间隔10秒 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(); } }
实验结果:
运行结束:
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())/*lambda表达式*/); 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。
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 H{ private static ArrayList<Mest> studentlist; public static void main(String[] args) { studentlist = new ArrayList<>(); Scanner scanner = new Scanner(System.in); File file = new File("C:\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(); Mest student = new Mest(); 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("1:字典排序"); System.out.println("2:输出年龄最大和年龄最小的人"); System.out.println("3:寻找老乡"); System.out.println("4:寻找年龄相近的人"); System.out.println("5:退出"); String m = scanner.next(); switch (m) { case "1": Collections.sort(studentlist); System.out.println(studentlist.toString()); break; case "2": 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 "3": System.out.println("家庭住址:"); 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("province"+studentlist.get(i)); } break; case "4": System.out.println("年龄:"); int yourage = scanner.nextInt(); int near=agematched(yourage); int value=yourage-studentlist.get(near).getage(); System.out.println(""+studentlist.get(near)); break; case "5": isTrue = false; System.out.println("退出程序!"); break; default: System.out.println("输入错误"); } } } public static int agematched(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; } }
public class M implements Comparable<M> { 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) { this.age= age; } public String getprovince() { return province; } public void setprovince(String province) { this.province=province ; } public int compareTo(M o) { return this.name.compareTo(o.getName()); } public String toString() { return name+" "+sex+" "+age+" "+number+" "+province+" "; } }
public class M implements Comparable<M> { 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) { this.age= age; } public String getprovince() { return province; } public void setprovince(String province) { this.province=province ; } public int compareTo(M o) { return this.name.compareTo(o.getName()); } public String toString() { return name+" "+sex+" "+age+" "+number+" "+province+" "; } }
实验结果:(字典排序)
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(); // 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。
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。
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;
三、实验总结
本次实验主要是为了掌握接口定义方法,实现接口类的定义要求, 实现了接口类的使用要求; 掌握程序回调设计模式,Comparator接口用法;掌握Lambda表达式语法;对于课文中的实验实例老师都讲的很清楚,理解的也比较好,但在操作实验中,尤其是:实验3: 编程练习,程序一直出不来,好多细节上还是很容易出错,希望在理解这些知识点的基础上可以有写进步。