Question

我的问题涉及在ArrayList中的对象中搜索特定变量并返回变量。其中一个问题是Student对象包含多个变量字段。

我试图在对象中找到一个特定的变量，然后从数组列表中返回它。

这是主要方法：

    Student s1 = new Student ("student1", 123, "MIS");
    Student s2 = new Student("student2", 231, "Finance");
    Student s3 = new Student ("student3", 432, "MIS");
    Student s4 = new Student ("student4", 438, "Marketing");
    Student s5 = new Student ("student5", 429, "MIS");
    Student s6 = new Student ("student6", 215, "Accounting");
    Student s7 = new Student ("student7", 287, "MIS");
    Student s8 = new Student ("student8", 401, "MIS");

    ArrayList<Student> myList = new ArrayList<Student>();
    myList.add(s1);
    myList.add(s2);
    myList.add(s3);
    myList.add(s4);
    myList.add(s5);
    myList.add(s6);
    myList.add(s7);
    myList.add(s8);

    StudentDatabaseImplementation st = new StudentDatabaseImplementation(); 
    st.setTheListOfStudents(myList);
    st.printTheListOfStudents(myList);


    st.getStudent(429);
    System.out.println("The name of the student : "+    
    st.getStudent(429).getName());

在我创建的Student课程中，我写道：

   public class Student{
   private String name;
   private int CWID, ID;
   private String major, maj;

   private ArrayList<Student> myList = new ArrayList<Student>()

   public Student(String name, int CWID, String major)
   {this.name=name;CWID=ID; String Major = maj;}

   public String getName() {return name;}

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

   public ArrayList<Student> getAllStudents() {return myList;}

   -->public Student getStudent(int CWID){if(myList.contains CWID)   
     {getName();}}

   public void setTheListOfStudents(ArrayList<Student> myList) {
   this.myList = myList;}

   public String getMajorName() {return majorName;}

   public void setMajorName(String majorName) {this.majorName = majorName;}

   public int getCWID() {return CWID;}

   public void setCWID(int studentId) {this.studentCWID = studentCWID;}

   private String majorName;
   private int studentCWID;

我还能做些什么来返回用户名吗？

Answer 1

虽然您的代码似乎没问题，但您可以覆盖toString()类的Student方法，并使其返回用户的名称。

public class Student {

    @Override
    public String toString() {
        return getName();
    }

}

然后你可以打电话

System.out.println("The name of the student : "+    
st.getStudent(429));

Answer 2

这是您应该如何实现getStudent方法。它返回null，如果找不到student，或者CWID等于CWID参数的学生，如果在列表中至少有Student具有该CWID。

public Student getStudent(int CWID){
    return myList.stream().filter(s -> s.getCWID()==CWID).findAny().orElse(null);
}

我建议您评估地图以存储学生。

Map<int,Student>

其中键是CWID。通过这种方式，你不应该迭代找到学生。

在ArrayList对象中引用特定变量

2 个答案: