201771010112羅鬆《面向物件程式設計（java）》第十週學習總結
阿新 • • 發佈：2018-11-04
實驗十
實驗時間 201
1、實驗目的與要求
(1) 理解泛型概念；
(2) 掌握泛型類的定義與使用；
(3) 掌握泛型方法的宣告與使用；
(4) 掌握泛型介面的定義與實現；
(5)瞭解泛型程式設計，理解其用途。
2、實驗內容和步驟
實驗1： 匯入第8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、除錯、執行教材311、312頁 程式碼，結合程式執行結果理解程式；
l 在泛型類定義及使用程式碼處添加註釋；
l 掌握泛型類的定義及使用。
程式碼：
package pair1; /** * @version 1.00 2004-05-10 * @author Cay Horstmann */ //泛型類使得類具有通用性 public class Pair<T> { private T first; private T second; public Pair() { first = null; second = null; } public Pair(T first, T second) { this.first = first; this.second = second; } public T getFirst() { return first; } public T getSecond() { return second; } public void setFirst(T newValue) { first = newValue; } public void setSecond(T newValue) { second = newValue; } package pair1;
package pair1; /** * @version 1.01 2012-01-26 * @author Cay Horstmann */ public class PairTest1 { public static void main(String[] args) { String[] words = { "Mary", "had", "a", "little", "lamb" }; Pair<String> mm = ArrayAlg.minmax(words);//泛型類物件String Pair類，靜態方法用類名呼叫方法,泛型字串型別，按字典序排序 System.out.println("min = " + mm.getFirst()); System.out.println("max = " + mm.getSecond()); } } class ArrayAlg { /** * Gets the minimum and maximum of an array of strings. * @param a an array of strings * @return a pair with the min and max value, or null if a is null or empty */ public static Pair<String> minmax(String[] a)//普通方法，返回值是一個例項化的Pair類物件 { if (a == null || a.length == 0) return null;//length是陣列的屬性值 String min = a[0]; String max = a[0]; for (int i = 1; i < a.length; i++) { if (min.compareTo(a[i]) > 0) min = a[i]; if (max.compareTo(a[i]) < 0) max = a[i]; } return new Pair<>(min, max);//用泛型類來返回兩個值 } }
結果：
測試程式2：
l 編輯、除錯執行教材315頁 PairTest2，結合程式執行結果理解程式；
l 在泛型程式設計程式碼處新增相關注釋；
l 掌握泛型方法、泛型變數限定的定義及用途。
程式碼：
package pair2; /** * @version 1.00 2004-05-10 * @author Cay Horstmann */ public class Pair<T> { private T first; private T second; public Pair() { first = null; second = null; } public Pair(T first, T second) { this.first = first; this.second = second; } public T getFirst() { return first; } public T getSecond() { return second; } public void setFirst(T newValue) { first = newValue; } public void setSecond(T newValue) { second = newValue; } }
package pair2; import java.time.*; /** * @version 1.02 2015-06-21 * @author Cay Horstmann */ public class PairTest2 { public static void main(String[] args) { LocalDate[] birthdays = { LocalDate.of(1906, 12, 9), // G. Hopper LocalDate.of(1815, 12, 10), // A. Lovelace LocalDate.of(1903, 12, 3), // J. von Neumann LocalDate.of(1910, 6, 22), // K. Zuse }; Pair<LocalDate> mm = ArrayAlg.minmax(birthdays); System.out.println("min = " + mm.getFirst()); System.out.println("max = " + mm.getSecond()); } } class ArrayAlg { /** Gets the minimum and maximum of an array of objects of type T. @param a an array of objects of type T @return a pair with the min and max value, or null if a is null or empty */ public static <T extends Comparable> Pair<T> minmax(T[] a) //泛型方法，有上界約束 { if (a == null || a.length == 0) return null; T min = a[0]; T max = a[0]; for (int i = 1; i < a.length; i++) { if (min.compareTo(a[i]) > 0) min = a[i]; if (max.compareTo(a[i]) < 0) max = a[i]; } return new Pair<>(min, max); } }
結果：
測試程式3：
l 用除錯執行教材335頁 PairTest3，結合程式執行結果理解程式；
l 瞭解萬用字元型別的定義及用途。
程式碼：
package pair3; /** * @version 1.00 2004-05-10 * @author Cay Horstmann */ public class Pair<T> { private T first; private T second; public Pair() { first = null; second = null; } public Pair(T first, T second) { this.first = first; this.second = second; } public T getFirst() { return first; } public T getSecond() { return second; } public void setFirst(T newValue) { first = newValue; } public void setSecond(T newValue) { second = newValue; } }
package pair3; import java.time.*; public class Employee { private String name; private double salary; private LocalDate hireDay; public Employee(String name, double salary, int year, int month, int day) { this.name = name; this.salary = salary; hireDay = LocalDate.of(year, month, day); } public String getName() { return name; } public double getSalary() { return salary; } public LocalDate getHireDay() { return hireDay; } public void raiseSalary(double byPercent) { double raise = salary * byPercent / 100; salary += raise; } }
package pair3; public class Manager extends Employee { private double bonus; /** @param name the employee's name @param salary the salary @param year the hire year @param month the hire month @param day the hire day */ public Manager(String name, double salary, int year, int month, int day) { super(name, salary, year, month, day); bonus = 0; } public double getSalary() { double baseSalary = super.getSalary(); return baseSalary + bonus; } public void setBonus(double b) { bonus = b; } public double getBonus() { return bonus; } }
package pair3; /** * @version 1.01 2012-01-26 * @author Cay Horstmann */ public class PairTest3 { public static void main(String[] args) { Manager ceo = new Manager("Gus Greedy", 800000, 2003, 12, 15); Manager cfo = new Manager("Sid Sneaky", 600000, 2003, 12, 15); Pair<Manager> buddies = new Pair<>(ceo, cfo); //型別變數 printBuddies(buddies); ceo.setBonus(1000000); cfo.setBonus(500000); Manager[] managers = { ceo, cfo }; Pair<Employee> result = new Pair<>();//也可以用Manager minmaxBonus(managers, result); System.out.println("first: " + result.getFirst().getName() + ", second: " + result.getSecond().getName()); maxminBonus(managers, result); System.out.println("first: " + result.getFirst().getName() + ", second: " + result.getSecond().getName()); } public static void printBuddies(Pair<? extends Employee> p)//上界約束 { Employee first = p.getFirst(); Employee second = p.getSecond(); System.out.println(first.getName() + " and " + second.getName() + " are buddies."); } public static void minmaxBonus(Manager[] a, Pair<? super Manager> result)//採用萬用字元來定義第二個型別變數result { if (a.length == 0) return; Manager min = a[0]; Manager max = a[0]; for (int i = 1; i < a.length; i++) { if (min.getBonus() > a[i].getBonus()) min = a[i]; if (max.getBonus() < a[i].getBonus()) max = a[i]; } result.setFirst(min); result.setSecond(max); } public static void maxminBonus(Manager[] a, Pair<? super Manager> result) { minmaxBonus(a, result); PairAlg.swapHelper(result); // OK--swapHelper captures wildcard type } // Can't write public static <T super manager> ... } class PairAlg { public static boolean hasNulls(Pair<?> p)//？型別變數的萬用字元，單獨的？表示任何一種型別，T表示一種未知型別 //將hasNulls轉換成泛型方法 //測試一個pair是否包含一個null引用 { return p.getFirst() == null || p.getSecond() == null; } //編寫一個交換成對元素的方法 public static void swap(Pair<?> p) { swapHelper(p); } public static <T> void swapHelper(Pair<T> p)//泛型方法 { T t = p.getFirst();//儲存第一個元素 p.setFirst(p.getSecond()); p.setSecond(t); } }
結果：
實驗2：程式設計練習：
程式設計練習1：實驗九程式設計題總結
l 實驗九程式設計練習1總結（從程式總體結構說明、模組說明，目前程式設計存在的困難與問題三個方面闡述）。
總體結構說明：
主類main，子類card
模組說明：
main
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 { /** * 1.檔案讀取模組 利用ArrayList構造studentlist存放檔案內容2. 建立檔案字元流，分類讀取檔案內容 3.try/catch語句捕獲異常 */ 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\\新建資料夾\\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 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("學生資訊檔案找不到"); e.printStackTrace(); // 加入的捕獲異常程式碼 } catch (IOException e) { System.out.println("學生資訊檔案讀取錯誤"); e.printStackTrace(); // 加入的捕獲異常程式碼 } /* * 1.根據實驗要求，選擇具體操作的模組 2.利用switch語句選擇具體的操作 */ boolean isTrue = true; while (isTrue) { System.out.println("選擇你的操作，輸入正確格式的選項"); System.out.println("A.字典排序"); System.out.println("B.輸出年齡最大和年齡最小的人"); System.out.println("C.尋找老鄉"); System.out.println("D.尋找年齡相近的人"); 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("年齡最大：" + studentlist.get(k1)); System.out.println("年齡最小：" + 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("老鄉" + studentlist.get(i)); } break; case "D": System.out.println("年齡："); 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("退出程式!"); break; default: System.out.println("輸入有誤"); } } } /* * 對年齡資料進行相應的處理 */ 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
card：
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 { /** * 1.檔案讀取模組 利用ArrayList構造studentlist存放檔案內容2. 建立檔案字元流，分類讀取檔案內容 3.try/catch語句捕獲異常 */ 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\\新建資料夾\\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 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("學生資訊檔案找不到"); e.printStackTrace(); // 加入的捕獲異常程式碼 } catch (IOException e) { System.out.println("學生資訊檔案讀取錯誤"); e.printStackTrace(); // 加入的捕獲異常程式碼 } /* * 1.根據實驗要求，選擇具體操作的模組 2.利用switch語句選擇具體的操作 */ boolean isTrue = true; while (isTrue) { System.out.println("選擇你的操作，輸入正確格式的選項"); System.out.println("A.字典排序"); System.out.println("B.輸出年齡最大和年齡最小的人"); System.out.println("C.尋找老鄉"); System.out.println("D.尋找年齡相近的人"); 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("年齡最大：" + studentlist.get(k1)); System.out.println("年齡最小：" + 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("老鄉" + studentlist.get(i)); } break; case "D": System.out.println("年齡："); 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("退出程式!"); break; default: System.out.println("輸入有誤"); } } } /* * 對年齡資料進行相應的處理 */ 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
問題：目前程式設計存在的困難與問題：讀檔案時，檔案路徑不正確，無法找到檔案。
l 實驗九程式設計練習2總結（從程式總體結構說明、模組說明，目前程式設計存在的困難與問題三個方面闡述）。
總體結構說明：
主類test和子類yunsuan
模組說明：
package demo; import java.io.PrintWriter; import java.util.Scanner; public class Test { public static void main(String[] args) { //檔案輸出模組，呼叫建構函式 @SuppressWarnings("resource") Scanner in = new Scanner(System.in); Demo demo=new Demo(); //建立檔案字元流，將output中的內容設為空（null） PrintWriter output = null; try { output = new PrintWriter("test.txt");//將out結果輸出到test.txt中 } catch (Exception e) { e.printStackTrace(); } int sum = 0; //定義一個sum，計算成績 //四則運算生成模組，生成10道題目 for (int i = 0; i < 10; i++) { int a = (int) Math.round(Math.random() * 100); int b = (int) Math.round(Math.random() * 100); int c = (int) Math.round(Math.random() * 3); switch (c) { case 0: System.out.println(a + "+" + b + "="); int d0 = in.nextInt(); output.println(a + "+" + b + "=" + d0); if (d0 == demo.demo1(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 1: while (a < b) { int x = a; a = b; b = x; } System.out.println(a + "-" + b + "="); int d1 = in.nextInt(); output.println(a + "-" + b + "=" + d1); if (d1 == demo.demo2(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 2: System.out.println(a + "*" + b + "="); int d2 = in.nextInt(); output.println(a + "*" + b + "=" + d2); if (d2 == demo.demo3(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 3: while (b == 0 || a % b != 0) { a = (int) Math.round(Math.random() * 100); b = (int) Math.round(Math.random() * 100); } System.out.println(a + "/" + b + "="); int d3 = in.nextInt(); output.println(a + "/" + b + "=" + d3); if (d3 == demo.demo4(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; } } System.out.println("你的得分為" + sum); output.println("你的得分為" + sum); //將迴圈結果輸出到test.txt中 output.close(); } } Test
package demo; public class yunsuan { private int a; private int b; public int add(int a,int b) { return a+b; } public int reduce(int a,int b) { return a-b; } public int multiplication(int a,int b) { return a*b; } public int division(int a,int b) { if(b!=0) return a/b; else return 0; } } yunsuan
問題：對printwrite不太瞭解。
程式設計練習2：採用泛型程式設計技術改進實驗九程式設計練習2，使之可處理實數四則運算，其他要求不變。
程式碼：
package demo; import java.io.PrintWriter; import java.util.Scanner; public class Test { public static void main(String[] args) { @SuppressWarnings("resource") Scanner in = new Scanner(System.in); Demo demo=new Demo(); PrintWriter output = null; try { output = new PrintWriter("test.txt"); } catch (Exception e) { e.printStackTrace(); } int sum = 0; for (int i = 0; i < 10; i++) { int a = (int) Math.round(Math.random() * 100); int b = (int) Math.round(Math.random() * 100); int c = (int) Math.round(Math.random() * 3); switch (c) { case 0: System.out.println(a + "+" + b + "="); int d0 = in.nextInt(); output.println(a + "+" + b + "=" + d0); if (d0 == demo.demo1(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 1: while (a < b) { int x = a; a = b; b = x; } System.out.println(a + "-" + b + "="); int d1 = in.nextInt(); output.println(a + "-" + b + "=" + d1); if (d1 == demo.demo2(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 2: System.out.println(a + "*" + b + "="); int d2 = in.nextInt(); output.println(a + "*" + b + "=" + d2); if (d2 == demo.demo3(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; case 3: while (b == 0 || a % b != 0) { a = (int) Math.round(Math.random() * 100); b = (int) Math.round(Math.random() * 100); } System.out.println(a + "/" + b + "="); int d3 = in.nextInt(); output.println(a + "/" + b + "=" + d3); if (d3 == demo.demo4(a, b)) { sum += 10; System.out.println("恭喜答案正確"); } else { System.out.println("抱歉，答案錯誤"); } break; } } System.out.println("你的得分為" + sum); output.println("你的得分為" + sum); output.close(); } } Test
package demo; public class yunsuan { private int a; private int b; public int add(int a,int b) { return a+b; } public int reduce(int a,int b) { return a-b; } public int multiplication(int a,int b) { return a*b; } public int division(int a,int b) { if(b!=0) return a/b; else return 0; } } yunsuan
結果：
實驗總結：通過這周的學習，我瞭解了泛型設計技術的概念，以及它的好處和限制，基本上會運用泛型技術設計程式，但是在很多知識的運用方面仍然不太懂，在之後的學習中要更加努力，課後要多練習，也希望老師能更加詳細的講解。