实验十一 集合
实验时间 2018-11-8
1、实验目的与要求
(1) 掌握Vetor、Stack、Hashtable三个类的用途及常用API；
Vector类类似长度可变的数组，其中只能存放对象，其中的元素通过下标进行访问。
Vetor类关键属性：
capacity表示集合最多能容纳的元素个数。
capacityIncrement表示每次增加多少容量。
siize集合当前元素个数。
Vector v = new Vector (100);
Stack是Vector的子类。
Stack类描述堆栈数据结构，即LIFO 。
Stack类的关键方法：
public void push(Object item)//把栈压入栈顶
public Object pop()//移除栈顶对象并作为此函数的值返回对象
public Object peek()//查看栈顶对象而不移除它
Public boolean empty()//推测堆栈是否为空
Hashtable通过键来查找元素。
Hastable用散列码（hastable）来确定键。所有对象都有有一个散列码，可以通过Object类的hastable()方法获得。
(2) 了解java集合框架体系组成；
(2) 掌握ArrayList、LinkList两个类的用途及常用API。
ArrayList可以将其看作是能够自动增长容量的数组。
利用ArrayList类的toArray返回一个数组。
Arrays.asList()返回一个列表。
LinkedList是采用双向循环列表实现的。
(4) 了解HashSet类、TreeSet类的用途及常用API。
(5)了解HashMap、TreeMap两个类的用途及常用API；
(6) 结对编程（Pair programming）练习，体验程序开发中的两人合作。
2、实验内容和步骤
实验1： 导入第9章示例程序，测试程序并进行代码注释。
测试程序1：
l 使用JDK命令运行编辑、运行以下三个示例程序，结合运行结果理解程序；
l 掌握Vetor、Stack、Hashtable三个类的用途及常用API。
出现运行时异常，输出Dog #7 时，类型不匹配。附上两种修改方法。
示例程序1：
package 小陈; import java.util.Vector; class Cat { private int catNumber; Cat(int i) { catNumber = i; } void print() { System.out.println("Cat #" + catNumber); } } class Dog { private int dogNumber; Dog(int i) { dogNumber = i; } void print() { System.out.println("Dog #" + dogNumber); } } public class CatsAndDogs { public static void main(String[] args) { Vector cats = new Vector(); for (int i = 0; i < 7; i++) cats.addElement(new Cat(i)); cats.addElement(new Dog(7)); for (int i = 0; i < cats.size()-1; i++) { System.out.println(cats.get(i).getClass());//获得类名 //if(cats.get(i).getClass() ) ((Cat) cats.elementAt(i)).print(); } System.out.println(cats.get(7).getClass());//获得类名 ((Dog) cats.elementAt(7)).print(); } } /*public class CatsAndDogs { public static void main(String[] args) { Vector cats = new Vector(); for (int i = 0; i < 7; i++) cats.addElement(new Cat(i)); cats.addElement(new Dog(7)); for (int i = 0; i < 7; i++) { System.out.println(cats.get(i).getClass());//获得类名 //if(cats.get(i).getClass() ) ((Cat) cats.elementAt(i)).print(); for ( i = 0; i < cats.size(); i++) { System.out.println(cats.get(i).getClass());//获得类名 //if(cats.get(i).getClass() ) ((Dog) cats.elementAt(i)).print(); } } System.out.println(cats.get(7).getClass());//获得类名 ((Dog) cats.elementAt(7)).print(); } }*/ /*public class CatsAndDogs { public static void main(String[] args) { Vector cats = new Vector(); for (int i = 0; i < 7; i++) cats.addElement(new Cat(i)); cats.addElement(new Dog(7)); for (int i = 0; i < cats.size(); i++) { System.out.println(cats.get(i).getClass());//获得类名 if(cats.elementAt(i) instanceof Cat) { ((Cat) cats.elementAt(i)).print(); }else { ((Dog) cats.elementAt(i)).print(); } } } }*/
运行结果：
示例程序2：
package 小陈3.src; import java.util.*; public class Stacks { static String[] months = { "1", "2", "3", "4" }; public static void main(String[] args) { Stack stk = new Stack(); for (int i = 0; i < months.length; i++) stk.push(months[i]); System.out.println(stk); System.out.println("element 2=" + stk.elementAt(2)); while (!stk.empty()) System.out.println(stk.pop()); } }
运行结果：
示例程序3：
package 小陈1; import java.util.*; class Counter { int i = 1;//不加任何访问权限修饰符，只允许在同一个包中进行访问。 public String toString() { return Integer.toString(i); } } public class Statistics { public static void main(String[] args) { Hashtable ht = new Hashtable();//生成哈希表类对象，哈希表存储的数据是键值 for (int i = 0; i < 10000; i++) { Integer r = new Integer((int) (Math.random() * 20)); //使用Math.random方法生成整型随机数r，范围是0到20 if (ht.containsKey(r)) //通过对象调用containsKey()，判断r值是否是哈希表里的键值，如果是，返回true，否则返回false ((Counter) ht.get(r)).i++;//获得哈希表里面的键值，引用Counter的属性，输出r出现的频次 else ht.put(r, new Counter());//调用put方法向哈希表里面添加键值 } System.out.println(ht); } }
运行结果：
测试程序3：
l 使用JDK命令编辑运行ArrayListDemo和LinkedListDemo两个程序，结合程序运行结果理解程序；
package 小陈3; import java.util.*; public class ArrayListDemo { public static void main(String[] argv) { ArrayList<Comparable> al = new ArrayList<Comparable>(); // Add lots of elements to the ArrayList... al.add(new Integer(11));//添加对象元素 al.add(new Integer(12)); al.add(new Integer(13)); al.add(new String("hello")); // First print them out using a for loop. System.out.println("Retrieving by index:"); //System.out.println(al.size());//输出al数组的长度 for (int i = 0; i < al.size(); i++) { System.out.println("Element " + i + " = " + al.get(i));//get方法存放索引值 } } }
运行结果：
package 小陈4; import java.util.*; public class LinkedListDemo { public static void main(String[] argv) { LinkedList l = new LinkedList();//构造一个空链表，实质为创建一个数组 l.add(new Object());//调用add方法向链表添加元素 l.add("Hello"); l.add("zhangsan"); ListIterator li = l.listIterator(0);//构造一个迭代器 while (li.hasNext()) //hasNext() 用于检查序列中是否还有元素，如果仍然有元素可以迭代，则返回true，返回迭代的下一个元素 System.out.println(li.next());//next()返回当前next()的一个对象 if (l.indexOf("Hello") < 0) System.err.println("Lookup does not work"); else System.err.println("Lookup works"); } }
运行结果：
l 在Elipse环境下编辑运行调试教材360页程序9-1，结合程序运行结果理解程序；
l 掌握ArrayList、LinkList两个类的用途及常用API。
package linkedList; import java.util.*; /** * This program demonstrates operations on linked lists. * @version 1.11 2012-01-26 * @author Cay Horstmann */ public class LinkedListTest { public static void main(String[] args) { List<String> a = new LinkedList<>();//构造一个空链表，实质为创建一个String类型的数组a a.add("Amy");//调用add方法向数组添加元素 a.add("Carl"); a.add("Erica"); List<String> b = new LinkedList<>(); b.add("Bob"); b.add("Doug"); b.add("Frances"); b.add("Gloria"); // merge the words from b into a，将a数组的内容合并到b中 ListIterator<String> aIter = a.listIterator(); //使用LinkList类的listIterator方法返回一个实现了listIterator接口的迭代器对象 Iterator<String> bIter = b.iterator(); while (bIter.hasNext()) { if (aIter.hasNext()) aIter.next(); aIter.add(bIter.next()); } System.out.println(a); // remove every second word from b，从b数组中删除第二个单词 bIter = b.iterator(); while (bIter.hasNext()) { bIter.next(); // skip one element if (bIter.hasNext()) { bIter.next(); // skip next element bIter.remove(); // remove that element } } System.out.println(b); // bulk operation: remove all words in b from a a.removeAll(b); System.out.println(a); } }
测试程序3：
l 运行SetDemo程序，结合运行结果理解程序；
package 小陈3.src; import java.util.*; public class SetDemo { public static void main(String[] argv) { HashSet h = new HashSet(); //也可以 Set h=new HashSet()
//构造一个空散列表 h.add("One"); h.add("Two"); h.add("One"); // DUPLICATE h.add("Three"); Iterator it = h.iterator(); while (it.hasNext()) { System.out.println(it.next()); } } }
运行结果：
l 在Elipse环境下调试教材365页程序9-2，结合运行结果理解程序；了解HashSet类的用途及常用API。
package set; import java.util.*; /** * This program uses a set to print all unique words in System.in. * @version 1.12 2015-06-21 * @author Cay Horstmann */ public class SetTest { public static void main(String[] args) { Set<String> words = new HashSet<>(); // HashSet implements Set，利用HashSet实现Set接口 long totalTime = 0; try (Scanner in = new Scanner(System.in)) { while (in.hasNext()) { String word = in.next(); long callTime = System.currentTimeMillis(); words.add(word); callTime = System.currentTimeMillis() - callTime; totalTime += callTime; } } Iterator<String> iter = words.iterator(); for (int i = 1; i <= 20 && iter.hasNext(); i++) System.out.println(iter.next()); System.out.println(". . ."); System.out.println(words.size() + " distinct words. " + totalTime + " milliseconds."); } }
运行结果：
l 在Elipse环境下调试教材367页-368程序9-3、9-4，结合程序运行结果理解程序；了解TreeSet类的用途及常用API。
package treeSet; import java.util.*; /** * This program sorts a set of item by comparing their descriptions. * @version 1.12 2015-06-21 * @author Cay Horstmann */ public class TreeSetTest { public static void main(String[] args) { SortedSet<Item> parts = new TreeSet<>();//构造一个空树集。 parts.add(new Item("Toaster", 1234)); parts.add(new Item("Widget", 4562)); parts.add(new Item("Modem", 9912)); System.out.println(parts); NavigableSet<Item> sortByDescription = new TreeSet<>( Comparator.comparing(Item::getDescription)); sortByDescription.addAll(parts); System.out.println(sortByDescription); } }
package treeSet; import java.util.*; /** * An item with a description and a part number. */ public class Item implements Comparable<Item> { private String description; private int partNumber; /** * Constructs an item. * * @param aDescription * the item's description * @param aPartNumber * the item's part number */ public Item(String aDescription, int aPartNumber) { description = aDescription; partNumber = aPartNumber; } /** * Gets the description of this item. * * @return the description */ public String getDescription() { return description; } public String toString() { return "[description=" + description + ", partNumber=" + partNumber + "]"; } public boolean equals(Object otherObject) { if (this == otherObject) return true; if (otherObject == null) return false; if (getClass() != otherObject.getClass()) return false; Item other = (Item) otherObject; return Objects.equals(description, other.description) && partNumber == other.partNumber; } public int hashCode() { return Objects.hash(description, partNumber); } public int compareTo(Item other) { int diff = Integer.compare(partNumber, other.partNumber); return diff != 0 ? diff : description.compareTo(other.description); } }
运行结果：
测试程序4：
l 使用JDK命令运行HashMapDemo程序，结合程序运行结果理解程序；
package treeSet; import java.util.*; public class HashMapDemo { public static void main(String[] argv) { HashMap h = new HashMap();//构造一个空散列映射 // The hash maps from company name to address. h.put("Adobe", "Mountain View, CA");//将这些元素插入到映射中 h.put("IBM", "White Plains, NY"); h.put("Sun", "Mountain View, CA"); String queryString = "Adobe"; String resultString = (String)h.get(queryString); System.out.println("They are located in: " + resultString); } }
运行结果：
l 在Elipse环境下调试教材373页程序9-6，结合程序运行结果理解程序；
了解HashMap、TreeMap两个类的用途及常用API。
package map; import java.util.*; /** * This program demonstrates the use of a map with key type String and value type Employee. * @version 1.12 2015-06-21 * @author Cay Horstmann */ public class MapTest { public static void main(String[] args) { Map<String, Employee> staff = new HashMap<>();//为存储的员工信息建立一个散列映射 staff.put("144-25-5464", new Employee("Amy Lee"));//a将员工信息添加到映射中 staff.put("567-24-2546", new Employee("Harry Hacker")); staff.put("157-62-7935", new Employee("Gary Cooper")); staff.put("456-62-5527", new Employee("Francesca Cruz")); // print all entries System.out.println(staff); // remove an entry staff.remove("567-24-2546"); // replace an entry staff.put("456-62-5527", new Employee("Francesca Miller")); // look up a value System.out.println(staff.get("157-62-7935")); // iterate through all entries staff.forEach((k, v) -> System.out.println("key=" + k + ", value=" + v)); } }
package map; /** * A minimalist employee class for testing purposes. */ public class Employee { private String name; private double salary; /** * Constructs an employee with $0 salary. * @param n the employee name */ public Employee(String name) { this.name = name; salary = 0; } public String toString() { return "[name=" + name + ", salary=" + salary + "]"; } }
运行结果：
实验2：结对编程练习：
l 关于结对编程：以下图片是一个结对编程场景：两位学习伙伴坐在一起，面对着同一台显示器，使用着同一键盘，同一个鼠标，他们一起思考问题，一起分析问题，一起编写程序。
l 关于结对编程的阐述可参见以下链接：
http://www.cnblogs.com/xinz/archive/2011/08/07/2130332.html
http://en.wikipedia.org/wiki/Pair_programming
l 对于结对编程中代码设计规范的要求参考：
http://www.cnblogs.com/xinz/archive/2011/11/20/2255971.html
以下实验，就让我们来体验一下结对编程的魅力。
l 确定本次实验结对编程合作伙伴；
l 各自运行合作伙伴实验九编程练习1，结合使用体验对所运行程序提出完善建议；
l 各自运行合作伙伴实验十编程练习2，结合使用体验对所运行程序提出完善建议；
l 采用结对编程方式，与学习伙伴合作完成实验九编程练习1；
l 采用结对编程方式，与学习伙伴合作完成实验十编程练习2。
合作伙伴：王燕
合作伙伴的代码：
身份证号文件处理：
package 看到谁; 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 Check{ 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:\\下载\\身份证号.txt");//文件读取 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) {//捕获异常 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(); } //加入异常处理机制，维护代码的健壮性 boolean isTrue = true; //选择所要进行的操作 while (isTrue) { System.out.println("选择你的操作，输入正确格式的选项"); System.out.println("1.按姓名字典序输出人员信息"); System.out.println("2.输出年龄最大和年龄最小的人"); System.out.println("3.查找老乡"); System.out.println("4.查找年龄相近的人"); 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("输入省份"); 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 "4": 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 "5": isTrue = false; System.out.println("退出程序!"); break; default: System.out.println("输入有误"); } } } 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; } }
package 看到谁; public class Student implements Comparable<Student> { 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()); }//对姓名进行字典排序 public String toString() { return name+"\t"+sex+"\t"+age+"\t"+number+"\t"+province+"\n"; } }
简易计算器：
package 看到谁; import java.io.FileNotFoundException; import java.io.PrintWriter; import java.util.Scanner; public class Caculator { public static void main(String[] args) { Scanner in = new Scanner(System.in); Caculator1 computing=new Caculator1(); PrintWriter output = null; //使用了异常处理机制，增强代码的安全性 try { output = new PrintWriter("Caculator.txt"); } catch (Exception e) { } int sum = 0; //随机数生成，提供后续题目所用的数据 for (int i = 1; i < 11; i++) { int a = (int) Math.round(Math.random() * 100); int b = (int) Math.round(Math.random() * 100); int s = (int) Math.round(Math.random() * 3); //选择所要进行的操作 switch(s)//s为随机数，可随机执行下面四种操作 { case 1: System.out.println(i+": "+a+"/"+b+"="); while(b==0){ b = (int) Math.round(Math.random() * 100); } double c = in.nextDouble(); output.println(a+"/"+b+"="+c); //修改建议:生成除法题目时，对a，b两个数进行条件判断，确保整除，还有除数不为0 if (c == (double)computing.division(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break; // case 2: System.out.println(i+": "+a+"*"+b+"="); int c1 = in.nextInt(); output.println(a+"*"+b+"="+c1); if (c1 == computing.multiplication(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break; case 3: System.out.println(i+": "+a+"+"+b+"="); int c2 = in.nextInt(); output.println(a+"+"+b+"="+c2); if (c2 == computing.addition(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break ; case 4: System.out.println(i+": "+a+"-"+b+"="); int c3 = in.nextInt(); output.println(a+"-"+b+"="+c3); if (c3 == computing.subtraction(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break ; } } System.out.println("scores："+sum); output.println("scores："+sum); output.close(); } } class Caculator1 { private int a; private int b; public int addition(int a,int b) { return a+b; } public int subtraction(int a,int b) { if((a-b)<0) return 0; else 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; } }
合作代码：
身份证号文件处理：
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 Identity{ 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:/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(); } 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("选择你的操作，输入正确格式的选项"); 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("0.退出"); int status = scanner.nextInt(); switch (status) { 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("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 4: 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 0: status = 0; System.out.println("程序已退出!"); break; default: System.out.println("输入错误"); } } } public static int agenear(int age) { int 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; } }
package 看到谁; public class Student implements Comparable<Student> { 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 ; } @Override public int compareTo(Student other) { // TODO Auto-generated method stub return this.name.compareTo(other.getName()); } public String toString() { return name+"\t"+sex+"\t"+age+"\t"+number+"\t"+province+"\n"; } }
运行结果：
简易计算器：
import java.io.FileNotFoundException; import java.io.PrintWriter; import java.util.Scanner; public class Caculator { public static void main(String[] args) { Scanner in = new Scanner(System.in); Caculator1 computing=new Caculator1(); PrintWriter output = null; try { output = new PrintWriter("Caculator.txt"); } catch (Exception e) { } int sum = 0; for (int i = 1; i < 11; i++) { int a = (int) Math.round(Math.random() * 100); int b = (int) Math.round(Math.random() * 100); int s = (int) Math.round(Math.random() * 3); switch(s) { case 1: System.out.println(i+": "+a+"/"+b+"="); while(b==0){ b = (int) Math.round(Math.random() * 100); } double c = in.nextDouble(); output.println(a+"/"+b+"="+c); if (c == (double)computing.division(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break; case 2: System.out.println(i+": "+a+"*"+b+"="); int c1 = in.nextInt(); output.println(a+"*"+b+"="+c1); if (c1 == computing.multiplication(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break; case 3: System.out.println(i+": "+a+"+"+b+"="); int c2 = in.nextInt(); output.println(a+"+"+b+"="+c2); if (c2 == computing.addition(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break ; case 4: System.out.println(i+": "+a+"-"+b+"="); int c3 = in.nextInt(); output.println(a+"-"+b+"="+c3); if (c3 == computing.subtraction(a, b)) { sum += 10; System.out.println("T"); } else { System.out.println("F"); } break ; } } System.out.println("scores："+sum); output.println("scores："+sum); output.close(); } } class Caculator1 { private int a; private int b; public int addition(int a,int b) { return a+b; } public int subtraction(int a,int b) { if((a-b)<0) return 0; else return a-b; } public int multiplication(int a,int b) { return a*b; } public int division(int a,int b) { if(b!=0 && a%b==0) return a/b; else return 0; } }
运行结果：
