TreeSet 和 TreeMap 排序 TreeSet对象和 TreeMap的Key必须实现Comparable 接口或Comparator接口
1、Comparable
引用Comparable 接口 必须实现其compareTo方法
public class Student implements Serializable,Comparable<Student>{
public String name;
public int age;
public Student(String name, int age) {
this.name = name;
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return "Student{" +
"name='" + name + '\'' +
", age=" + age +
'}';
}
@Override
public int compareTo(Student o) {
if(null == o) return -1;
return this.getAge() - o.getAge();
}
2、Comparator
只拿TreeSet举例了
//
TreeSet<Student> treeSet = new TreeSet(new Comparator() {
@Override
public int compare(Object o1, Object o2) {
Student s1 = (Student) o1;
Student s2 = (Student) o2;
if (s1.getAge() > s2.getAge()) return 1;
if(s1.getAge() < s2.getAge()) return -1;
if(s2.getAge() == s1.getAge()) return s1.getName().compareTo(s2.getName());
return 1;
}
});