201771010119窮吉第八週
實驗六 介面的定義與使用
實驗時間 2018-10-18
理論知識:
介面體中包含常量定義和方法定義,介面中只進行方法的宣告,不提供方法的實現。
類似建立類的繼承關係,介面也可以擴充套件。介面的擴充套件技術使得從具有較高通用性的介面存在多條鏈延伸到具有較高專用性的介面。
通常介面的名字以able或ible結尾;可以使用extends來繼承介面的常量和抽象方法,擴充套件形成新的介面;介面中的所有常量必須是public static final,方法必須是public abstract,這是系統預設的,不管你在定義介面時,寫不寫修飾符都是一樣的。
一個類使用了某個介面,那麼這個類必須實現該介面的所有方法,即為這些方法提供方法體。一個類可以實現多個介面,介面間應該用逗號分隔開。例:class Employee implements Cloneable,Comparable
若實現介面的類不是抽象類,則必須實現所有介面的所有方法,即為所有的抽象方法定義方 法體。一個類在實現某介面抽象方法時,必須使用完全相同的方法名、引數列表和返回值型別。介面抽象方法的訪問控制符已指定為public, 所以類在實現時,必須顯式地使用public修飾符,否則被警告縮小了介面中定義的方法的訪問控制範圍。
介面不能構造介面物件,但可以宣告介面變數以指向一個實現了該介面的類物件。可以用instanceof檢查物件是否實現了某個介面
物件克隆
Object類的Clone方法
Object類的clone()方法是一個native方法。
Object類中的 clone()方法被protected修飾符修飾。 這意味著在使用者編寫的程式碼中不能直接呼叫它。如果要直接應用clone()方法,就需 覆蓋clone()方法,並要把clone()方法的屬性設定為 public。
Object.clone()方法返回一個Object物件。必須進行強 制型別轉換才能得到需要的型別。
Lambda 表示式的語法基本結構 (arguments) -> body
1、實驗目的與要求
(1) 掌握介面定義方法;
(2) 掌握實現介面類的定義要求;
(3) 掌握實現了介面類的使用要求;
(4) 掌握程式回撥設計模式;
(5) 掌握Comparator介面用法;
(6) 掌握物件淺層拷貝與深層拷貝方法;
(7) 掌握Lambda表示式語法;
(8) 瞭解內部類的用途及語法要求。
2、實驗內容和步驟
實驗1: 匯入第6章示例程式,測試程式並進行程式碼註釋。
測試程式1:
l 編輯、編譯、除錯執行閱讀教材214頁-215頁程式6-1、6-2,理解程式並分析程式執行結果;
l 在程式中相關程式碼處新增新知識的註釋。
l 掌握介面的實現用法;
l 掌握內建介面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); //輸出所有關於Employee物件的資訊 for (Employee e : staff) System.out.println("name=" + e.getName() + ",salary=" + e.getSalary()); } }
第二
package interfaces;
public class Employee implements Comparable<Employee>
//建立一個泛型Comparable介面,提供一個型別引數,比較Employee類的物件並進行排序 { 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);//運用double呼叫compare來進行比較 //salary的大小兩兩互相比較,升序排出salary的大小 } }
結果:
測試程式2:
l 編輯、編譯、除錯以下程式,結合程式執行結果理解程式
interface A
{
double g=9.8;
void show( );
}
class C implements A
//對C使用A介面的方法
{
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);
}
結果;
測試程式3:
l 在elipse IDE中除錯執行教材223頁6-3,結合程式執行結果理解程式;
l 26行、36行程式碼參閱224頁,詳細內容涉及教材12章。
l 在程式中相關程式碼處新增新知識的註釋。
l 掌握回撥程式設計模式
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();// ActionListener listener被new TimePrinter介面引用
// 構造一個timer物件存放在變數裡,叫做listener
// 每次間隔10秒
Timer t = new Timer(10000, listener);
t.start();//用T呼叫start物件
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(); //每隔10秒響一次
}
}
結果:
測試程式4:
l 除錯執行教材229頁-231頁程式6-4、6-5,結合程式執行結果理解程式;
l 在程式中相關程式碼處新增新知識的註釋。
l 掌握物件克隆實現技術;
l 掌握淺拷貝和深拷貝的差別。
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 //放入try中,配合後面的語句捕獲異常 { 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) //捕獲異常 { 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 + "]"; } }
結果“
實驗2: 匯入第6章示例程式6-6,學習Lambda表示式用法。
l 除錯執行教材233頁-234頁程式6-6,結合程式執行結果理解程式;
l 在程式中相關程式碼處新增新知識的註釋。
l 將27-29行程式碼與教材223頁程式對比,將27-29行程式碼與此程式對比,體會Lambda表示式的優點。
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); } }
結果:
實驗3: 程式設計練習
l 編制一個程式,將身份證號.txt 中的資訊讀入到記憶體中;
l 按姓名字典序輸出人員資訊;
l 查詢最大年齡的人員資訊;
l 查詢最小年齡人員資訊;
l 輸入你的年齡,查詢身份證號.txt中年齡與你最近人的姓名、身份證號、年齡、性別和出生地;
查詢人員中是否有你的同鄉。
package ID; public class Person implements Comparable<Person> { 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) { 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(Person o) { return this.name.compareTo(o.getname()); } public String toString() { return name+"\t"+sex+"\t"+age+"\t"+ID+"\t"+birthplace+"\n"; } } package ID; 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<Person> Personlist; public static void main(String[] args) { Personlist = new ArrayList<>(); Scanner scanner = new Scanner(System.in); File file = new File("C:\\mydirectory\\身份證號.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(); Person Person = new Person(); Person.setname(name); Person.setID(ID); Person.setsex(sex); int a = Integer.parseInt(age); Person.setage(a); Person.setbirthplace(place); Personlist.add(Person); } } catch (FileNotFoundException e) { System.out.println("查詢不到資訊"); e.printStackTrace(); } catch (IOException e) { System.out.println("資訊讀取有誤"); e.printStackTrace(); } boolean isTrue = true; while (isTrue) { System.out.println("1:按姓名字典序輸出人員資訊"); System.out.println("2:查詢最大年齡與最小年齡人員資訊"); System.out.println("3:按省份找同鄉"); System.out.println("4:輸入你的年齡,查詢年齡與你最近人的資訊"); System.out.println("5:退出"); int nextInt = scanner.nextInt(); switch (nextInt) { case 1: Collections.sort(Personlist); System.out.println(Personlist.toString()); break; case 2: int max=0,min=100;int j,k1 = 0,k2=0; for(int i=1;i<Personlist.size();i++) { j=Personlist.get(i).getage(); if(j>max) { max=j; k1=i; } if(j<min) { min=j; k2=i; } } System.out.println("年齡最大:"+Personlist.get(k1)); System.out.println("年齡最小:"+Personlist.get(k2)); break; case 3: System.out.println("省份?"); String find = scanner.next(); String place=find.substring(0,3); String place2=find.substring(0,3); for (int i = 0; i <Personlist.size(); i++) { if(Personlist.get(i).getbirthplace().substring(1,4).equals(place)) System.out.println("同鄉 "+Personlist.get(i)); } break; case 4: System.out.println("年齡:"); int yourage = scanner.nextInt(); int near=agenear(yourage); int d_value=yourage-Personlist.get(near).getage(); System.out.println(""+Personlist.get(near)); break; case 5: isTrue = false; System.out.println("歡迎使用!"); break; default: System.out.println("輸入有誤"); } } } public static int agenear(int age) { int j=0,min=53,d_value=0,k=0; for (int i = 0; i < Personlist.size(); i++) { d_value=Personlist.get(i).getage()-age; if(d_value<0) d_value=-d_value; if (d_value<min) { min=d_value; k=i; } } return k; } }
實驗4:內部類語法驗證實驗
實驗程式1:
l 編輯、除錯執行教材246頁-247頁程式6-7,結合程式執行結果理解程式;
l 瞭解內部類的基本用法。
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(); } } }
結果:
實驗程式2:
l 編輯、除錯執行教材254頁程式6-8,結合程式執行結果理解程式;
l 瞭解匿名內部類的用法。
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(); } }
結果:
實驗程式3:
l 在elipse IDE中除錯執行教材257頁-258頁程式6-9,結合程式執行結果理解程式;
l 瞭解靜態內部類的用法。
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); } }
結果:
實驗總結:通過這次學習瞭解了介面的定義和介面的種種知識,還有克隆和拷貝知識。