201771010120 蘇浪浪 面向物件程式設計(Java)第10周
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。
package pair1; /** * @version 1.00 2004-05-10 *@author Cay Horstmann */ public class Pair<T> //引入型別變數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() { returnsecond; } public void setFirst(T newValue) { first = newValue; } public void setSecond(T newValue) { second = newValue; } }
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); System.out.println("min = " + mm.getFirst()); System.out.println("max = " + mm.getSecond()); } } class ArrayAlg//泛型方法 { /** * 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) { if (a == null || a.length == 0) return null; 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); } }
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。
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。
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)。
1程式總體分為兩個類、三個模組具體如下:
package aaa; 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 b{ private static ArrayList<Student> studentlist; public static void main(String[] args) { studentlist = new ArrayList<>(); Scanner scanner = new Scanner(System.in); File file = new File("身份證號.txt");//檔案的匯入模組 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(); } catch (IOException e) { System.out.println("學生資訊檔案讀取錯誤"); e.printStackTrace(); } boolean isTrue = true; while (isTrue) { //選擇模組 System.out.println("選擇你的操作, "); System.out.println("1.字典排序 "); System.out.println("2.輸出年齡最大和年齡最小的人 "); System.out.println("3.尋找老鄉 "); System.out.println("4.尋找年齡相近的人 "); 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("年齡最大:"+studentlist.get(k1)); System.out.println("年齡最小:"+studentlist.get(k2)); break; case "3": System.out.println("地址?"); 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("老鄉"+studentlist.get(i)); } break; case "4": 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 "5 ": isTrue = false; System.out.println("退出程式!"); break; default: System.out.println("輸入有誤"); } } } public static int agenear(int age) { int j=0,min=53,value=0,ok=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; ok=i; } } return ok; } }
package aaa; public class Student implements Comparable<Student> {//介面模組 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"; } }
目前存在的問題:檔案讀入的地址可能出現錯誤,介面的定義也可能出現問題;演算法的實現也可能會出問題。
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)。
1程式總體分為兩個類、三個模組具體如下:
package duanyan; import java.io.FileNotFoundException; import java.io.PrintWriter; import java.util.Scanner; public class z { public static void main(String[] args) { Scanner in = new Scanner(System.in); Student student=new Student(); PrintWriter out = null; try { out = new PrintWriter("text.txt");//儲存檔案模組 } catch (FileNotFoundException e) { e.printStackTrace(); } int sum = 0; //隨機生成a、b的值以及隨機的運算模組 for (int i = 1; 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(i+": "+a+"/"+b+"="); while(b==0) { b = (int) Math.round(Math.random() * 100); } int C = in.nextInt(); out.println(a+"/"+b+"="+C); if (C == student.d(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: System.out.println(i+": "+a+"*"+b+"="); int D = in.nextInt(); out.println(a+"*"+b+"="+D); if (D == student.m(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(i+": "+a+"+"+b+"="); while(a<b) { a = (int) Math.round(Math.random() * 100); } int E = in.nextInt(); out.println(a+"+"+b+"="+E); if (E == student.add(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: System.out.println(i+": "+a+"-"+b+"="); int F = in.nextInt(); out.println(a+"-"+b+"="+F); if (F == student.r(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("成績"+sum); out.println("成績:"+sum); out.close(); } }
package duanyan; public class Student { 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; } }
存在問題的:演算法的實現可能出現錯誤,子類的定義可能出現錯誤,除法運算中被除數b不能等於0可能會考慮不到,減法運算中a>b可能會注意不到,
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。
package 算; import java.io.FileNotFoundException; import java.io.PrintWriter; import java.util.Scanner; public class z { public static void main(String[] args) { Scanner in = new Scanner(System.in); Student student=new Student(); PrintWriter out = null; try { out = new PrintWriter("text.txt"); } catch (FileNotFoundException e) { e.printStackTrace(); } int sum = 0; for (int i = 1; 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(i+": "+a+"/"+b+"="); while(b==0) { b = (int) Math.round(Math.random() * 100); } int C = in.nextInt(); out.println(a+"/"+b+"="+C); if (C == student.d(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: System.out.println(i+": "+a+"*"+b+"="); int D = in.nextInt(); out.println(a+"*"+b+"="+D); if (D == student.m(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(i+": "+a+"+"+b+"="); while(a<b) { a = (int) Math.round(Math.random() * 100); } int E = in.nextInt(); out.println(a+"+"+b+"="+E); if (E == student.add(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: System.out.println(i+": "+a+"-"+b+"="); int F = in.nextInt(); out.println(a+"-"+b+"="+F); if (F == student.r(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("成績"+sum); out.println("成績:"+sum); out.close(); } }
package 算; public class Student<T> { private T a; private T b; public Student() { a = null; b = null; } public Student(T a, T b) { this.a = a; this.b = b; } public int add(int a,int b) { return a+b; } public int r(int a,int b) { return a-b; } public int m(int a,int b) { return a*b; } public int d(int a,int b) { return a/b; } }
實驗總結:本章學習了泛型程式設計,泛型程式設計可以讓程式更可讀、更安全。它捨棄了不安全的強制轉換型別;通過老師與主教學長的幫助,知道了什麼是泛型程式設計,也知道了萬用字元是什麼;在本次的實驗中野實踐了泛型程式設計。