java - 如何修复 java 中不需要的新行？

Question

我想弄清楚为什么每次在 for 循环中调用返回方法时我的代码都会创建一个新行。主 for 循环中的 if 语句检查名为 list 的数组列表中的每个学生对象。完成比较学生 i 和学生 j 之后(学生 j 是第二个 for 循环)。一旦 Student i 找到了最佳匹配，它应该打印出一条声明，说明他/她已经与某人匹配。

这是应该返回的内容:

Abey matches with Melissa with score 60
John matches with Jeff with score 100
Craig has no matches.

相反，它返回:

Abey matches with 
Melissa with score 60

John matches with 
Jeff with score 100

Craig has no matches.

代码如下:

    for (int i = 0; i < list.size(); i++) {
    int maxScore = 0;
    int currentScore = 0;
    int bestMatchScore = 0;
    int bestMatchStudent = 0;
    if (!list.get(i).isMatched()) {
        for (int j = i; j < list.size(); j++) {
            if (!list.get(j).isMatched()) {
                if (j != i) {
                currentScore = list.get(i).compare(list.get(j));
                if (currentScore > maxScore) {
                    maxScore = currentScore;
                    bestMatchStudent = j;
                    bestMatchScore = maxScore;
                }
                }
            }
        }
            if(bestMatchScore == 0) {
                System.out.println(list.get(i).getName() + " has no matches.");
                }
            else {
                list.get(i).setMatched(list.get(bestMatchStudent));

                System.out.println(list.get(i).getName() + " matches with " + list.get(bestMatchStudent).getName() + " with score " + maxScore);
            }
        }
    }

如果我要删除 if-else 语句中的所有 getName()，我会得到一个我想要的输出:

Student@6d3552ed matches with Student@47d77d9e with score 60
Student@147834eb matches with Student@5fda3acc with score 100
Student@704a583d has no matches. 

我怀疑它与调用 getName 方法有关。它只是一个访问器方法...

这里是重现问题的所有代码:

学生类(class)

public class Student {
    private String name;
    private char gender;
    private Date birthdate;
    private Preference pref;
    private boolean matched;

public Student(String name, char gender, Date birthdate, Preference pref) {
    this.name = name;
    this.gender = gender;
    this.birthdate = birthdate;
    this.pref = pref;
}

public String getName() {
    return name;
}

public char getGender() {
    return gender;
}

public Date getBirthdate() {
    return birthdate;
}

public Preference getPref() {
    return pref;
}

public boolean isMatched() {
    return matched;
}

public void setMatched() {
    this.matched = true;
}

public void setMatched(Student roommate) {
    setMatched();
    roommate.setMatched();
}

public int compare(Student st) {
    if (st.getGender() != gender)
        return 0;       
    return Math.abs((40 - pref.compare(st.getPref())) + (60 - birthdate.compare(st.getBirthdate())));
}

}

匹配类

import java.io.*;
import java.util.Scanner;
import java.util.*;
public class Match {

public static void main(String[] args) throws FileNotFoundException {
    //Student[] fullRoster = new Student[5]; converted to ArrayList
    ArrayList<Student> list = new ArrayList<Student>();
    String fileName = "Students.txt";
    Scanner input = new Scanner(new FileReader(fileName));
    input.useDelimiter("[\t\r-]");
    //int studentIndex = 0; converted to ArrayList
    while(input.hasNext()) {
        String name = input.next();
        //System.out.println(name);
        char gender = input.next().charAt(0);
        //System.out.println(gender);
        int month = Integer.parseInt(input.next());
        //System.out.println(month);
        int day = Integer.parseInt(input.next());
        //System.out.println(day);
        int year = Integer.parseInt(input.next());
        //System.out.println(year);
        Date birthday = new Date(year, month, day);
        //System.out.println(birthday); //Printed out birthday
        int pref1 = Integer.parseInt(input.next());
        //System.out.println(pref1);
        int pref2 = Integer.parseInt(input.next());
        //System.out.println(pref2);
        int pref3 = Integer.parseInt(input.next());
        //System.out.println(pref3);
        int pref4 = Integer.parseInt(input.next());
        //System.out.println(pref4);
        Preference pref = new Preference(pref1, pref2, pref3, pref4);
        //System.out.println(pref); //Printed out pref
        //fullRoster[studentIndex] = new Student(name, gender, birthday, pref); converted to ArrayList
        list.add(new Student(name, gender, birthday, pref));
        //studentIndex++; converted to ArrayList                
    }

    input.close();

    for (int i = 0; i < list.size(); i++) {
    int maxScore = 0;
    int currentScore = 0;
    int bestMatchScore = 0;
    int bestMatchStudent = 0;
    if (!list.get(i).isMatched()) {
        for (int j = i; j < list.size(); j++) {
            if (!list.get(j).isMatched()) {
                if (j != i) {
                currentScore = list.get(i).compare(list.get(j));
                if (currentScore > maxScore) {
                    maxScore = currentScore;
                    bestMatchStudent = j;
                    bestMatchScore = maxScore;
                }
                }
            }
        }
            if(bestMatchScore == 0) {
                System.out.println(list.get(i) + " has no matches.");
                }
            else {
                list.get(i).setMatched(list.get(bestMatchStudent));

                System.out.println(list.get(i).getName() + " matches with " + list.get(bestMatchStudent) + " with score " + maxScore);
            }
        }
    }
}
}

偏好等级

public class Preference {
private int quietTime, music, reading, chatting;

public Preference(int quietTime, int music, int reading, int chatting) {
    this.quietTime = quietTime;
    this.music = music;
    this.reading = reading;
    this.chatting = chatting;
}

public int getQuietTime() {
    return quietTime;
}

public int getMusic() {
    return music;
}

public int getReading() {
    return reading;
}

public int getChatting() {
    return chatting;
}

public int compare(Preference pref) {
    int difference = 0;
    difference += Math.abs(pref.getQuietTime() - this.getQuietTime());
    difference += Math.abs(pref.getMusic() - this.getMusic());
    difference += Math.abs(pref.getReading() - this.getReading());
    difference += Math.abs(pref.getChatting() - this.getChatting());
    return difference;
}

}

日期类

public class Date {
int year, month, day;

public Date(int year, int month, int day) {
    this.year = year;
    this.month = month;
    this.day = day;
}

public int getYear() {
    return year;
}

public int getMonth() {
    return month;
}

public int getDay() {
    return day;
}

public int compare(Date dt) {
    int yearsDifferenceInDays = (Math.abs(year - dt.getYear())) * 365;
    int daysDifference = Math.abs(dt.dayOfYear() - this.dayOfYear());
    int totalDifference = Math.abs(yearsDifferenceInDays - daysDifference);
    int monthsDifference = totalDifference / 30;
    if(monthsDifference > 60)
        return 60;
    return monthsDifference;
}

public int dayOfYear() {
    int totalDays = 0;
    switch (month) {
    case 12: totalDays += 30;
    case 11: totalDays += 31;
    case 10: totalDays += 30;
    case 9 : totalDays += 31;
    case 8 : totalDays += 31;
    case 7 : totalDays += 30;
    case 6 : totalDays += 31;
    case 5 : totalDays += 30;
    case 4 : totalDays += 31;
    case 3 : totalDays += 28;
    case 2 : totalDays += 31;
    }
    totalDays += day;
    return totalDays;
    }
}

匹配类

import java.io.*;
import java.util.Scanner;
import java.util.*;

public class Match {

public static void main(String[] args) throws FileNotFoundException {
    //Student[] fullRoster = new Student[5]; converted to ArrayList
    ArrayList<Student> list = new ArrayList<Student>();
    String fileName = "Students.txt";
    Scanner input = new Scanner(new FileReader(fileName));
    input.useDelimiter("[\t\r-]");
    //int studentIndex = 0; converted to ArrayList
    while(input.hasNext()) {
        String name = input.next();
        //System.out.println(name);
        char gender = input.next().charAt(0);
        //System.out.println(gender);
        int month = Integer.parseInt(input.next());
        //System.out.println(month);
        int day = Integer.parseInt(input.next());
        //System.out.println(day);
        int year = Integer.parseInt(input.next());
        //System.out.println(year);
        Date birthday = new Date(year, month, day);
        //System.out.println(birthday); //Printed out birthday
        int pref1 = Integer.parseInt(input.next());
        //System.out.println(pref1);
        int pref2 = Integer.parseInt(input.next());
        //System.out.println(pref2);
        int pref3 = Integer.parseInt(input.next());
        //System.out.println(pref3);
        int pref4 = Integer.parseInt(input.next());
        //System.out.println(pref4);
        Preference pref = new Preference(pref1, pref2, pref3, pref4);
        //System.out.println(pref); //Printed out pref
        //fullRoster[studentIndex] = new Student(name, gender, birthday, pref); converted to ArrayList
        list.add(new Student(name, gender, birthday, pref));
        //studentIndex++; converted to ArrayList                
    }

    input.close();

    for (int i = 0; i < list.size(); i++) {
    int maxScore = 0;
    int currentScore = 0;
    int bestMatchScore = 0;
    int bestMatchStudent = 0;
    if (!list.get(i).isMatched()) {
        for (int j = i; j < list.size(); j++) {
            if (!list.get(j).isMatched()) {
                if (j != i) {
                currentScore = list.get(i).compare(list.get(j));
                if (currentScore > maxScore) {
                    maxScore = currentScore;
                    bestMatchStudent = j;
                    bestMatchScore = maxScore;
                }
                }
            }
        }
            if(bestMatchScore == 0) {
                System.out.println(list.get(i) + " has no matches.");
                }
            else {
                list.get(i).setMatched(list.get(bestMatchStudent));

                System.out.println(list.get(i).getName() + " matches with " + list.get(bestMatchStudent) + " with score " + maxScore);
            }
        }
    }
}
}

Students.txt

Abey    F   5-5-1996    0   0   0   0
John    M   5-5-1997    10  10  10  10
Melissa F   5-5-1996    10  10  10  10
Craig   M   5-5-1998    5   5   5   5
Jeff    M   5-5-1997    10  10  10  10

Answer 1

If I were to remove all of the getName() inside the if-else statement, I get an output that is sort of what I desire:

Student@6d3552ed matches with Student@47d77d9e with score 60
Student@147834eb matches with Student@5fda3acc with score 100
Student@704a583d has no matches.

此处解释了该输出 How do I print my Java object without getting "SomeType@2f92e0f4"?

看来您只需要trim() 名称即可。

根据您希望在哪里执行“输入验证”，您可以在输入时执行此操作。

String name = input.next().trim();

或者在构造函数中

public Student(String name, char gender, Date birthdate, Preference pref) {
    this.name = name.trim();
    this.gender = gender;
    this.birthdate = birthdate;
    this.pref = pref;
}

或者在 setter/getter 中

public String getName() {
    return name.trim();
}

或者当你实际在 println

中显示值时

或者定义toString()，正如在另一篇文章中解释的那样return name.trim();，然后打印list.get(i) ，就像你所做的那样。

---

根本问题可能是您没有将 LF (\n) 或 CRLF (\r\n) 定义为分隔符。

input.useDelimiter("[\t\r-]");

尝试

input.useDelimiter("\r\n|[\t\r\n-]");