Java compareTo方法初学者

Question

null

public class Student implements Comparable{

private String nep_c;
private int point_num;
private int Mark;

public Student(int point_num, String nep_c) {
    this.point_num = 65;
    this.nep_c= "AAA1BB1";
}

public int getMark(){
    if (point_num <= 100 && point_num > 90)
    Mark = 5;
    else if (point_num <= 90 && point_num > 80)
    Mark = 4;
    else if (point_num <= 80 && point_num > 70)
    Mark = 3;
    else if (point_num <= 70 && point_num > 60)
    Mark = 2;
    else if (point_num <= 60)
    Mark = 1;
    else{
        return 0;
    }
    return Mark;
}

public String getNep_c(){
    return nep_c;
}

public int getPoint_num(){
    return point_num;
}

@Override
public int compareTo (Object o){
    return ???;
}

}

Answer 1

根据neptun代码对学生进行排序

两部分。第一部分，改变

implements Comparable

到

implements Comparable<Student>

@Override
public int compareTo(Student o) {
    return this.nep_c.compareTo(o.nep_c);
}

@Override
public int compareTo(Student o) {
    return Integer.compare(getMark(), o.getMark());
}

int c = this.nep_c.compareTo(o.nep_c);
if (c != 0) {
    return c;
}
return Integer.compare(getMark(), o.getMark());

return Comparator.comparing(Student::getNep_c)
        .thenComparingInt(Student::getMark).compare(this, o);