在您现有的学生类的基础上,这是我通常的做法,特别是当我需要多个比较器时。
public class Student implements Comparable<Student> {
String name;
int age;
public Student(String name, int age) {
this.name = name;
this.age = age;
}
@Override
public String toString() {
return name + ":" + age;
}
@Override
public int compareTo(Student o) {
return Comparators.NAME.compare(this, o);
}
public static class Comparators {
public static Comparator<Student> NAME = new Comparator<Student>() {
@Override
public int compare(Student o1, Student o2) {
return o1.name.compareTo(o2.name);
}
};
public static Comparator<Student> AGE = new Comparator<Student>() {
@Override
public int compare(Student o1, Student o2) {
return o1.age - o2.age;
}
};
public static Comparator<Student> NAMEANDAGE = new Comparator<Student>() {
@Override
public int compare(Student o1, Student o2) {
int i = o1.name.compareTo(o2.name);
if (i == 0) {
i = o1.age - o2.age;
}
return i;
}
};
}
}
使用方法:
List<Student> studentList = new LinkedList<>()
Collections.sort(studentList, Student.Comparators.AGE)
编辑
自从Java 8发布以来,使用lambda表达式可以大大简化内部类Comparators
的代码。Java 8还引入了一个新的方法thenComparing
用于Comparator
对象,当嵌套比较器时,它可以省去手动检查每个比较器的需要。以下是考虑到这些更改的Student.Comparators
类的Java 8实现。
public static class Comparators {
public static final Comparator<Student> NAME = (Student o1, Student o2) -> o1.name.compareTo(o2.name);
public static final Comparator<Student> AGE = (Student o1, Student o2) -> Integer.compare(o1.age, o2.age);
public static final Comparator<Student> NAMEANDAGE = (Student o1, Student o2) -> NAME.thenComparing(AGE).compare(o1, o2);
}