Question

如何比较学生对象

我的代码

如何比较学生对象如何比较学生对象
如何比较学生对象如何比较学生对象

import java.time.format.DateTimeFormatter;
import java.util.Comparator;

public class Student implements Comparable < Student >{

    private String studentName;
    private String studentDOJ;

    public String getStudentName() {
        return studentName;
    }
    public void setStudentName(String studentName) {
        this.studentName = studentName;
    }
    public String getStudentDOJ() {
        return studentDOJ;
    }
    public void setStudentDOJ(String studentDOJ) {
        this.studentDOJ = studentDOJ;
    }


  @Override
        public int compareTo(Student other) {
             DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
             return Comparator.comparing(LocalDate.parse(Student::getStudentDOJ,formatter)).reversed()
                     .compare(this, other);
        }

}

Answer 1

您不能在此处使用方法引用。

LocalDate.parse(CharSequence, DateTimeFormatter)不需要Function<Student, String>，因此您不能通过Student::getStudentDOJ。

@Override
public int compareTo(Student other) {
  DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
  return Comparator.comparing((Student student) -> LocalDate.parse(student.getStudentDOJ(), formatter)).reversed()
      .compare(this, other);
}

Answer 2

您可以这样重写方法：

@Override
public int compareTo(Student other) {
    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd-MM-yyyy");
    return LocalDate.parse(getStudentDOJ(),formatter)
            .compareTo(LocalDate.parse(other.getStudentDOJ(),formatter));
}

并且可以将List<Student>类型的学生列表排序为：

lists.sort(Comparator.reverseOrder()); // dsc
lists.sort(Comparator.naturalOrder()); // asc

如何比较学生对象

2 个答案: