String[] arr = "张三,15,20".split(","); Student stu =new Student(arr[0],Integer.parseInt(arr[1],arr[2]));哪里错误

在创建 Student 对象时，Integer.parseInt() 方法只接受一个参数，但是在这里传递了两个参数。应该将代码修改为:

String[] arr = "张三,15,20".split(",");
Student stu = new Student(arr[0], Integer.parseInt(arr[1]), Integer.parseInt(arr[2]));

这样就可以正确地将字符串中的数字转换为整数，并创建一个新的 Student 对象。

相关问题

帮我解释以下代码import java.io.*; import java.time.LocalDate; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; public class Demo5 { public static void main(String[] args) throws IOException { ArrayList<Student> arr = new ArrayList<>(); File f1 = new File("input.txt"); FileInputStream fin = new FileInputStream(f1); BufferedReader br = new BufferedReader(new InputStreamReader(fin)); String msg = br.readLine(); while (msg != null) { if (msg.equals("")) { msg = br.readLine(); continue; } String[] stu = msg.split(" "); String num = stu[0]; String na = stu[1]; String da = stu[2]; String gen = stu[3]; Student student = new Student(Integer.parseInt(num), na,LocalDate.parse(da), gen); arr.add(student); Collections.sort(arr,Comparator.comparing(Student::getDate)); msg = br.readLine(); } br.close(); fin.close(); FileWriter writer = new FileWriter("output.txt"); for (Student obj:arr ) { writer.write(String.valueOf(obj)); writer.write("\r\n"); } writer.close(); } static class Student { private Integer number; private String name; private LocalDate date; private String gender; public LocalDate getDate() { return date; } public Student(Integer number, String name, LocalDate date, String gender) { this.number = number; this.name = name; this.date = date; this.gender = gender; } @Override public String toString() { return number + " " + name + " " + date + " " + gender; } } }

这段代码主要实现了以下功能：

1. 从名为"input.txt"的文件中读取学生信息，每一行为一名学生的信息，包括学号、姓名、出生日期和性别，用空格分隔。
2. 将读取的学生信息存储在一个ArrayList中，每个元素为一个Student对象。
3. 对ArrayList中的学生对象按照出生日期进行排序。
4. 将排好序的学生信息写入名为"output.txt"的文件中，每行为一名学生的信息，格式与输入文件相同。

其中，Student类表示一个学生对象，包括学号、姓名、出生日期和性别属性，并且重写了toString()方法以便于输出。通过LocalDate类来处理日期信息，Comparator.comparing()方法用于比较出生日期并进行排序。

将如下题按LinkedList集合或HashSet集合各实现一次。在HashSet中需重写hashCode()和equals()方法来判断元素是否重复。 按要求完成下列操作： 1、创建一个学生类（包含学号，姓名，性别，年龄属性，无参及有参构造函数） 2、创建两个集合 对象 arr1和arr2 3、向arr1集合中添加学生对象stu1("2001","zhangsan","男",19),stu2("2002","lisi","男",20),查看集合的长度 4、向arr2集合中添加学生对象stu3("2003","zhang","男",19),stu4("2004","lisi","女",20)，查看集合的长度 5、将arr1的元素复制到arr2中，查看arr2集合的长度 6、删除arr2中索引1的元素并查看其值 7、移除arr1中所有的元素java

使用LinkedList集合实现：

import java.util.LinkedList;

public class Student {
    private String id;
    private String name;
    private String gender;
    private int age;

    public Student() {}

    public Student(String id, String name, String gender, int age) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                '}';
    }
}

public class Main {
    public static void main(String[] args) {
        LinkedList<Student> arr1 = new LinkedList<>();
        LinkedList<Student> arr2 = new LinkedList<>();

        // 向arr1中添加学生对象
        Student stu1 = new Student("2001", "zhangsan", "男", 19);
        Student stu2 = new Student("2002", "lisi", "男", 20);
        arr1.add(stu1);
        arr1.add(stu2);
        System.out.println("arr1的长度为：" + arr1.size());

        // 向arr2中添加学生对象
        Student stu3 = new Student("2003", "zhang", "男", 19);
        Student stu4 = new Student("2004", "lisi", "女", 20);
        arr2.add(stu3);
        arr2.add(stu4);
        System.out.println("arr2的长度为：" + arr2.size());

        // 将arr1的元素复制到arr2中
        arr2.addAll(arr1);
        System.out.println("复制后arr2的长度为：" + arr2.size());

        // 删除arr2中索引1的元素并查看其值
        Student removed = arr2.remove(1);
        System.out.println("被删除的元素为：" + removed);

        // 移除arr1中所有的元素
        arr1.clear();
        System.out.println("arr1的长度为：" + arr1.size());
    }
}

使用HashSet集合实现：

import java.util.HashSet;
import java.util.Objects;

public class Student {
    private String id;
    private String name;
    private String gender;
    private int age;

    public Student() {}

    public Student(String id, String name, String gender, int age) {
        this.id = id;
        this.name = name;
        this.gender = gender;
        this.age = age;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getGender() {
        return gender;
    }

    public void setGender(String gender) {
        this.gender = gender;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id='" + id + '\'' +
                ", name='" + name + '\'' +
                ", gender='" + gender + '\'' +
                ", age=" + age +
                '}';
    }

    @Override
    public int hashCode() {
        return Objects.hash(id, name, gender, age);
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) return true;
        if (obj == null || getClass() != obj.getClass()) return false;
        Student student = (Student) obj;
        return age == student.age &&
                Objects.equals(id, student.id) &&
                Objects.equals(name, student.name) &&
                Objects.equals(gender, student.gender);
    }
}

public class Main {
    public static void main(String[] args) {
        HashSet<Student> arr1 = new HashSet<>();
        HashSet<Student> arr2 = new HashSet<>();

        // 向arr1中添加学生对象
        Student stu1 = new Student("2001", "zhangsan", "男", 19);
        Student stu2 = new Student("2002", "lisi", "男", 20);
        arr1.add(stu1);
        arr1.add(stu2);
        System.out.println("arr1的长度为：" + arr1.size());

        // 向arr2中添加学生对象
        Student stu3 = new Student("2003", "zhang", "男", 19);
        Student stu4 = new Student("2004", "lisi", "女", 20);
        arr2.add(stu3);
        arr2.add(stu4);
        System.out.println("arr2的长度为：" + arr2.size());

        // 将arr1的元素复制到arr2中
        arr2.addAll(arr1);
        System.out.println("复制后arr2的长度为：" + arr2.size());

        // 删除arr2中索引1的元素并查看其值
        int index = 1;
        Student removed = null;
        for (Student student : arr2) {
            if (index == 1) {
                removed = student;
                break;
            }
            index++;
        }
        arr2.remove(removed);
        System.out.println("被删除的元素为：" + removed);

        // 移除arr1中所有的元素
        arr1.clear();
        System.out.println("arr1的长度为：" + arr1.size());
    }
}