实验十 泛型程序设计技术
实验时间 2018-11-4
1、实验目的与要求
(1) 理解泛型概念；
(2) 掌握泛型类的定义与使用；
(3) 掌握泛型方法的声明与使用；
(4) 掌握泛型接口的定义与实现；
(5)了解泛型程序设计，理解其用途。
2、实验内容和步骤
实验1： 导入第8章示例程序，测试程序并进行代码注释。
测试程序1：
l 编辑、调试、运行教材311、312页 代码，结合程序运行结果理解程序；
l 在泛型类定义及使用代码处添加注释；
l 掌握泛型类的定义及使用。
代码：
package pair1;
/**
* @version 1.00 2004-05-10
* @author Cay Horstmann
*/
//泛型类使得类具有通用性
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);//泛型类对象String Pair类，静态方法用类名调用方法,泛型字符串类型，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，返回值是一个实例化的Pair类对象
{
if (a == null || a.length == 0) return null;//length是数组的属性值
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);//用泛型类来返回两个值
}
}
结果：
测试程序2：
l 编辑、调试运行教材315页 PairTest2，结合程序运行结果理解程序；
l 在泛型程序设计代码处添加相关注释；
l 掌握泛型方法、泛型变量限定的定义及用途。
代码：
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，有上界约束
{
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);
}
}
结果：
测试程序3：
l 用调试运行教材335页 PairTest3，结合程序运行结果理解程序；
l 了解通配符类型的定义及用途。
代码：
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); //类型变量
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)//上界约束
{
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)//采用通配符来定义第二个类型变量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)//？类型变量的通配符，单独的？表示任何一种类型，T表示一种未知类型
//将hasNulls转换成泛型方法
//测试一个pair是否包含一个null引用
{
return p.getFirst() == null || p.getSecond() == null;
}
//编写一个交换成对元素的方法
public static void swap(Pair<?> p) { swapHelper(p); }
public static <T> void swapHelper(Pair<T> p)//泛型方法
{
T t = p.getFirst();//保存第一个元素
p.setFirst(p.getSecond());
p.setSecond(t);
}
}
结果：
实验2：编程练习：
编程练习1：实验九编程题总结
l 实验九编程练习1总结（从程序总体结构说明、模块说明，目前程序设计存在的困难与问题三个方面阐述）。
总体结构说明：
主类main，子类card
模块说明：
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.文件读取模块 利用ArrayList构造studentlist存放文件内容2. 创建文件字符流，分类读取文件内容 3.try/catch语句捕获异常
*/
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\\新建文件夹\\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();
// 加入的捕获异常代码
} catch (IOException e) {
System.out.println("学生信息文件读取错误");
e.printStackTrace();
// 加入的捕获异常代码
}
/*
* 1.根据实验要求，选择具体操作的模块 2.利用switch语句选择具体的操作
*/
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("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 "F":
isTrue = false;
System.out.println("退出程序!");
break;
default:
System.out.println("输入有误");
}
}
}
/*
* 对年龄数据进行相应的处理
*/
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.文件读取模块 利用ArrayList构造studentlist存放文件内容2. 创建文件字符流，分类读取文件内容 3.try/catch语句捕获异常
*/
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\\新建文件夹\\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();
// 加入的捕获异常代码
} catch (IOException e) {
System.out.println("学生信息文件读取错误");
e.printStackTrace();
// 加入的捕获异常代码
}
/*
* 1.根据实验要求，选择具体操作的模块 2.利用switch语句选择具体的操作
*/
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("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 "F":
isTrue = false;
System.out.println("退出程序!");
break;
default:
System.out.println("输入有误");
}
}
}
/*
* 对年龄数据进行相应的处理
*/
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
问题：目前程序设计存在的困难与问题：读文件时，文件路径不正确，无法找到文件。
l 实验九编程练习2总结（从程序总体结构说明、模块说明，目前程序设计存在的困难与问题三个方面阐述）。
总体结构说明：
主类test和子类yunsuan
模块说明：
package demo;
import java.io.PrintWriter;
import java.util.Scanner;
public class Test {
public static void main(String[] args) {
//文件输出模块，调用构造函数
@SuppressWarnings("resource")
Scanner in = new Scanner(System.in);
Demo demo=new Demo();
//创建文件字符流，将output中的内容设为空（null）
PrintWriter output = null;
try {
output = new PrintWriter("test.txt");//将out结果输出到test.txt中
} catch (Exception e) {
e.printStackTrace();
}
int sum = 0; //定义一个sum，计算成绩
//四则运算生成模块，生成10道题目
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
break;
}
}
System.out.println("你的得分为" + sum);
output.println("你的得分为" + sum); //将循环结果输出到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
问题：对printwrite不太了解。
编程练习2：采用泛型程序设计技术改进实验九编程练习2，使之可处理实数四则运算，其他要求不变。
代码：
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
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("恭喜答案正确");
} else {
System.out.println("抱歉，答案错误");
}
break;
}
}
System.out.println("你的得分为" + sum);
output.println("你的得分为" + 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
结果：
实验总结：通过这周的学习，我了解了泛型设计技术的概念，以及它的好处和限制，基本上会运用泛型技术设计程序，但是在很多知识的运用方面仍然不太懂，在之后的学习中要更加努力，课后要多练习，也希望老师能更加详细的讲解。
原文地址：https://www.cnblogs.com/xuezhiqian/p/9903574.html
时间： 2024-10-13 20:48:35