在这里，我想收集子字符串后的所有内容并将其设置为特定字段。
import java.util.ArrayList;
import java.util.Scanner;
import java.io.File;
import java.io.FileNotFoundException;
/**
*
*
* class StudentReader for retrieveing data from file
*
*/
public class StudentReader {
public static Student[] readFromTextFile(String fileName) {
ArrayList<Student> result = new ArrayList<Student>();
File f = new File(filename);
Scanner n = new Scanner(f);
while (n.hasNextLine()) {
String text = n.nextLine();
}
n.close();
String hold1[] = text.Split(",");
String hold2[] = new String[hold1.length];;
for(int i = 0; i < hold1.length(); ++i) {
hold2[i] = hold1.Split("=");
if (hold2[i].substring(0,3).equals("name")) {
}
}
return result.toArray(new Student[0]);
}
}
备份此代码的目标是首先打开并读取一个文件，该文件包含大约20行，如下所示 学生{name = Jill Gall，年龄= 21，gpa = 2.98} 然后，我需要像上面那样将其拆分，首先两次以去除逗号和等号，然后针对每一行收集名称，年龄和双精度值，将其解析，然后将其设置为新的学生对象并返回它们将要保存到的数组，我目前遇到的问题是我无法弄清楚这里是什么用于收集“名称”，“年龄”，“ gpa”之后的所有内容的正确代码，因为我不知道如何设置不同名称的特定子字符串 即时通讯使用此链接作为参考，但我看不出它到底在做什么
答案 0 :(得分：0)
我认为错误在于以下几行
while (n.hasNextLine()) {
String text = n.nextLine();
}
由于文本是while循环中的局部变量，因此上述代码应在String hold1[] = text.Split(",");处引发编译错误。
实际上应该是
List<String> inputs = new ArrayList<String>()
Scanner n = new Scanner(f);
while (n.hasNextLine()) {
inputs.add(n.nextLine());
}
您可以使用上方inputs的列表来操作您的逻辑
答案 1 :(得分：0)
从外观上看，至少在ArrayList <>声明中，您有一个名为 Student 的类，该类包含 studentName 的成员变量实例。 em>， studentAge 和 studentGPA 。可能看起来像这样（ Getter / Setter 方法当然是可选的，被覆盖的 toString（）方法也是可选的）：
public class Student {
// Member Variables...
String studentName;
int studentAge = 0;
double studentGPA = 0.0d;
// Constructor 1:
public Student() { }
// Constructor 2: (used to fill instance member variables
// right away when a new instance of Student is created)
public Student(String name, int age, double gpa) {
this.studentName = name;
this.studentAge = age;
this.studentGPA = gpa;
}
// Getters & Setters...
public String getStudentName() {
return studentName;
}
public void setStudentName(String studentName) {
this.studentName = studentName;
}
public int getStudentAge() {
return studentAge;
}
public void setStudentAge(int studentAge) {
this.studentAge = studentAge;
}
public double getStudentGPA() {
return studentGPA;
}
public void setStudentGPA(double studentGPA) {
this.studentGPA = studentGPA;
}
@Override
public String toString() {
return new StringBuilder("").append(studentName).append(", ")
.append(String.valueOf(studentAge)).append(", ")
.append(String.valueOf(studentGPA)).toString();
}
}
我应该认为目标是从学生文本文件中读取每个文件行，其中每个文件行均包含特定学生的姓名，学生的年龄和学生的GPA分数，并为该学生创建一个Student实例在该特定文件行上。直到文件结束为止。如果“学生”文本文件中有20个学生，则 readFromTextFile（）方法运行完成后，将有20个特定的Student实例。您的 StudentReader 类可能看起来像这样：
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;
/**
*
* class StudentReader for retrieving data from file
*
*/
public class StudentReader {
private static final Scanner userInput = new Scanner(System.in);
private static Student[] studentsArray;
public static void main(String args[]) {
String underline = "=====================================================";
String dataFilePath = "StudentsFile.txt";
System.out.println("Reading in Student data from file named: " + dataFilePath);
if (args.length >= 1) {
dataFilePath = args[0].trim();
if (!new File(dataFilePath).exists()) {
System.err.println("Data File Not Found! (" + dataFilePath + ")");
return;
}
}
studentsArray = readFromTextFile(dataFilePath);
System.out.println("Displaying student data in Console Window:");
displayStudents();
System.out.println(underline);
System.out.println("Get all Student's GPA score average:");
double allGPA = getAllStudentsGPAAverage();
System.out.println("GPA score average for all Students is: --> " +
String.format("%.2f",allGPA));
System.out.println(underline);
System.out.println("Get a Student's GPA score:");
String sName = null;
while (sName == null) {
System.out.print("Enter a student's name: --> ");
sName = userInput.nextLine();
/* Validate that it is a name. Should validate in
almost any language including Hindi. From Stack-
Overflow post: https://stackoverflow.com/a/57037472/4725875 */
if (sName.matches("^[\\p{L}\\p{M}]+([\\p{L}\\p{Pd}\\p{Zs}'.]*"
+ "[\\p{L}\\p{M}])+$|^[\\p{L}\\p{M}]+$")) {
break;
}
else {
System.err.println("Invalid Name! Try again...");
System.out.println();
sName = null;
}
}
boolean haveName = isStudent(sName);
System.out.println("Do we have an instance of "+ sName +
" from data file? --> " +
(haveName ? "Yes" : "No"));
// Get Student's GPA
if (haveName) {
double sGPA = getStudentGPA(sName);
System.out.println(sName + "'s GPA score is: --> " + sGPA);
}
System.out.println(underline);
}
public static Student[] readFromTextFile(String fileName) {
List<Student> result = new ArrayList<>();
File f = new File(fileName);
try (Scanner input = new Scanner(f)) {
while (input.hasNextLine()) {
String fileLine = input.nextLine().trim();
if (fileLine.isEmpty()) {
continue;
}
String[] lineParts = fileLine.split("\\s{0,},\\s{0,}");
String studentName = "";
int studentAge = 0;
double studentGPA = 0.0d;
// Get Student Name (if it exists).
if (lineParts.length >= 1) {
studentName = lineParts[0].split("\\s{0,}\\=\\s{0,}")[1];
// Get Student Age (if it exists).
if (lineParts.length >= 2) {
String tmpStrg = lineParts[1].split("\\s{0,}\\=\\s{0,}")[1];
// Validate data.
if (tmpStrg.matches("\\d+")) {
studentAge = Integer.valueOf(tmpStrg);
}
// Get Student GPA (if it exists).
if (lineParts.length >= 3) {
tmpStrg = lineParts[2].split("\\s{0,}\\=\\s{0,}")[1];
// Validate data.
if (tmpStrg.matches("-?\\d+(\\.\\d+)?")) {
studentGPA = Double.valueOf(tmpStrg);
}
}
}
}
/* Create a new Student instance and pass the student's data
into the Student Constructor then add the Student instance
to the 'result' List. */
result.add(new Student(studentName, studentAge, studentGPA));
}
}
catch (FileNotFoundException ex) {
System.err.println(ex);
}
return result.toArray(new Student[result.size()]);
}
public static void displayStudents() {
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return;
}
for (int i = 0; i < studentsArray.length; i++) {
System.out.println(studentsArray[i].toString());
}
}
public static boolean isStudent(String studentsName) {
boolean found = false;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return found;
} else if (studentsName == null || studentsName.isEmpty()) {
System.err.println("Student name can not be Null or Null-String (\"\")!");
return found;
}
for (int i = 0; i < studentsArray.length; i++) {
if (studentsArray[i].getStudentName().equalsIgnoreCase(studentsName)) {
found = true;
break;
}
}
return found;
}
public static double getStudentGPA(String studentsName) {
double score = 0.0d;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return score;
} else if (studentsName == null || studentsName.isEmpty()) {
System.err.println("Student name can not be Null or Null-String (\"\")!");
return score;
}
boolean found = false;
for (int i = 0; i < studentsArray.length; i++) {
if (studentsArray[i].getStudentName().equalsIgnoreCase(studentsName)) {
found = true;
score = studentsArray[i].getStudentGPA();
break;
}
}
if (!found) {
System.err.println("The Student named '" + studentsName + "' could not be found!");
}
return score;
}
public static double getAllStudentsGPAAverage() {
double total = 0.0d;
if (studentsArray == null || studentsArray.length == 0) {
System.err.println("There are no Students within the supplied Students Array!");
return total;
}
for (int i = 0; i < studentsArray.length; i++) {
total += studentsArray[i].getStudentGPA();
}
return total / (double) studentsArray.length;
}
}