如何编写读取数组列表中特定内容并计算数组内容数量的方法

Question

我是一个新的学习者，我应该创建一个方法来使这个程序完全没有问题地运行，这样我就可以得到如下所示的 :::final 结果:::
3是3
马克就是马克
理查德就是理查德

这是代码（请阅读我在代码中写的 cmets）

public class Main {

/*I wrote the following method (Student) but I keep get some issues:
Please help I spend many days and I can't figure it out and I am runnung out
of time as I should understand the problem or at least the correction that I
can read and figure out what I was doing wrong.*/

// My written code starts here
    public static String Student(String[] sx){
        int counter = 0;
        for (int i = 0; i < sx.length; i ++){
            if (sx[i] != null)  counter ++;
        }
        return counter;
        sx = new String[counter];
    }
// My written code ENDS here

    // From this point I should preserve the code without any changes 
    static Student studentA;
    static Student studentB;
    static Student studentC;

    public static void main(String[] args) {
        studentA = new Student("Mark", "John", "Jimmy");
        studentB = new Student("Will", "George", "Androw");
        studentC = new Student("Frank", "Sam");
        int totalStudents = Student.getTotalStudents();
        System.out.println(totalStudents + " is 3");
        System.out.println(studentA.getFirstName() + " is Mark");
        studentA.setFirstName("Richard");
        System.out.println(studentA.getFirstName() + " is Richard");
    }
}

Answer 1

检查以下代码sn-p

import java.util.List;

public class Main {

    // My written code starts here
    static class Student {
        String firstName;
        String middleName;
        String lastName;

        // Constructor for setting the class variable with all 3 field
        public Student(String firstName, String middleName, String lastName) {
            this.firstName = firstName;
            this.middleName = middleName;
            this.lastName = lastName;
        }

        // Constructor for setting the class variable with 2 field
        public Student(String firstName, String lastName) {
            this.firstName = firstName;
            this.lastName = lastName;
        }

        //to get the FirstName field of a student object
        public String getFirstName() {
            return firstName;
        }

        //to set the FirstName field of a student object
        public void setFirstName(String firstName) {
            this.firstName = firstName;
        }

        public static int getTotalStudents() {
            // this is wrong way of doing this. 
            // You should ideally send a list Of Student to know the number of students as shown below
            return 3;
        }

        public static int getTotalStudentsFromList(List<Student> studentList) {
            return studentList.size();
        }

    }
// My written code ENDS here

    // From this point I should preserve the code without any changes
    static Student studentA;
    static Student studentB;
    static Student studentC;

    public static void main(String[] args) {
        studentA = new Student("Mark", "John", "Jimmy");
        studentB = new Student("Will", "George", "Androw");
        studentC = new Student("Frank", "Sam");
        int totalStudents = Student.getTotalStudents();
        System.out.println(totalStudents + " is 3");
        System.out.println(studentA.getFirstName() + " is Mark");
        studentA.setFirstName("Richard");
        System.out.println(studentA.getFirstName() + " is Richard");
    }
}

我添加了可能的 cmets 来解释代码。如果您对理解有任何困难，请告诉我。