我很想知道如何计算“插入”“删除”“搜索”和“打印”功能中的比较。该程序需要的是它可以将“学生”添加到列表中，从列表中删除它们，打印列表以及其他功能。但是，它需要能够计算插入，删除，搜索和打印时进行的比较。我知道这需要一个for循环，但我不能完全正确。有什么建议吗？
以下是我的代码（警告，它很大）：
import java.io.*;
import java.util.*;
import javax.swing.JOptionPane;
public class Assignment3{
static String students = ""; //Records of matching students
static int matches = 0; //Number of matching students
static Set <Student> names = new HashSet<Student>(); //HashSet to store Students
public static void main(String[] args) throws FileNotFoundException{
int ID = 0;
String lastName;
double GPA;
boolean run = true;
while (run == true){
String menu = JOptionPane.showInputDialog(null, "1) Loading students" +
"\n2) Adding new student" +
"\n3) Removing student " +
"\n4) Searching students" +
"\n5) Printing students " +
"\n6) Quit");
//Loading students from a text file
if (menu.equals("1")){
String inputFileName = JOptionPane.showInputDialog(null, "Input file:");
File inputFile = new File(inputFileName);
Scanner in = new Scanner(inputFile);
while (in.hasNext()){ //Loading names from text file to array!
ID = in.nextInt();
lastName = in.next();
GPA = in.nextDouble();
Student student = new Student(ID,lastName,GPA);
names.add(student);
}
in.close(); //Done loading from file, closing input!
}
//Adding more students to your list
if (menu.equals("2")){
String idString = JOptionPane.showInputDialog(null, "Please Enter an ID for student");
ID = Integer.parseInt(idString);
lastName = JOptionPane.showInputDialog(null, "Please enter a last name for student");
String gpaString = JOptionPane.showInputDialog(null, "Please enter a GPA for student");
GPA = Double.parseDouble(gpaString);
Student student = new Student(ID,lastName,GPA);
names.add(student);
}
//Remove student
if (menu.equals("3")){
String idString = JOptionPane.showInputDialog(null, "Please enter an ID for student to remove");
deleteStudentByID(Integer.parseInt(idString),names);
}
//Search
if (menu.equals("4")){
String searchMenu = JOptionPane.showInputDialog(null, "1) Search by ID" +
"\n2) Search by name" +
"\n3) Search by GPA");
if (searchMenu.equals("1")){
int count = 0;
for (int n=1; n<ID; n++)
count++; // insert a[n] into a[0..(n-1)]
String idSearch = JOptionPane.showInputDialog(null, "Please enter ID number");
JOptionPane.showMessageDialog(null, "Found " + (findStudentByID(Integer.parseInt(idSearch),names) + " Student\n" + students));
System.out.println("The number of comparisons is " + count );
}
if (searchMenu.equals("2")){
String nameSearch = JOptionPane.showInputDialog(null, "Enter last name");
JOptionPane.showMessageDialog(null, "Found: " + findStudentByName(nameSearch,names) + "\n" + matches + " student(s) with last name of " + nameSearch);
}
if (searchMenu.equals("3")){
String gpaSearch = JOptionPane.showInputDialog(null, "Enter GPA");
JOptionPane.showMessageDialog(null, "Found " + (findStudentByGPA(Double.parseDouble(gpaSearch),names) + " Student(s)\n" + students));
}
}
//Print
if (menu.equals("5")){
String printMenu = JOptionPane.showInputDialog(null, "1) Print to console" +
"\n2) Print to file");
//Console
if (printMenu.equals("1")){
Iterator <Student> iter = names.iterator();
while (iter.hasNext()){
Student tempStudent = iter.next();
System.out.println("ID: " + tempStudent.getID() + " Name: " + tempStudent.getName() + " GPA: " + tempStudent.getGPA() + " Hash Code: " + tempStudent.hashCode());
}
JOptionPane.showMessageDialog(null,"Output to console complete");
}
//Text file
if (printMenu.equals("2")){
String outputFileName = JOptionPane.showInputDialog(null, "Output file:");
PrintWriter out = new PrintWriter(outputFileName);
Iterator <Student> iter = names.iterator();
while (iter.hasNext()){
Student tempStudent = iter.next();
out.println("ID: " + tempStudent.getID() + " Name: " + tempStudent.getName() + " GPA: " + tempStudent.getGPA() + " Hash Code: " + tempStudent.hashCode());
}
out.close(); //Done writing to file, close output
JOptionPane.showMessageDialog(null,"Output saved to " + outputFileName);
}
}
//Quit
if (menu.equals("6")){
System.exit(0);
}
}
}
//Delete a student
static void deleteStudentByID(int id, Set <Student> list){
matches = 0;
students = "";
Iterator<Student> iterator = names.iterator();
while (iterator.hasNext()) {
Student student = iterator.next();
if (student.getIDHash() == Integer.toString(id).hashCode()){
matches++;
students = "ID: " + student.getID() + " Name: " + student.getName() + " GPA: " + student.getGPA() + "\n";
list.remove(student);
JOptionPane.showMessageDialog(null, "Deleted " + matches + " Student\n" + students);
break;
}
}
if (matches == 0){
JOptionPane.showMessageDialog(null,"Student not found");
}
}
//Search by ID
static int findStudentByID(int id,Set <Student> list){
matches = 0;
students = "";
for (Student student : list){
if (student.getIDHash() == Integer.toString(id).hashCode()){
matches++;
students = "ID: " + student.getID() + " Name: " + student.getName() + " GPA: " + student.getGPA() + "\n";
}
}
return matches;
}
//Search by name
static String findStudentByName(String name,Set <Student> list){
matches = 0;
students = "";
for (Student student : list) {
if (student.getNameHash() == name.hashCode()){
matches++;
}
}
if (matches > 0){
return "YES";
}
return "NO";
}
//Search by GPA
static double findStudentByGPA(double gpa,Set <Student> list){
matches = 0;
students = "";
for (Student student : list){
if (student.getGPAHash() == Double.toString(gpa).hashCode()){
matches++;
students += "ID: " + student.getID() + " Name: " + student.getName() + " GPA: " + student.getGPA() + "\n";
}
}
return matches;
}
}
答案 0 :(得分：0)
只要有一个反变量，比如说：
int count;
并在每次程序进行比较时递增它。
答案 1 :(得分：0)
我建议将Chain of Responsibility模式与Abstract Method结合使用。
换句话说，您的示例根本不是面向对象的。你正在进行函数式编程，这就是为什么这个计数意味着严重的代码重复（在许多地方你必须做count++）。介绍Comparison类和AbstractComparison实现链。