我试图按名称按字母顺序对Person进行排序,然后按年龄按升序排序
我可以按名称的相反顺序排序,但无法按年龄的升序排序。
PerId Name Age
--------------
7 Simpson 8
3 Michel 10
9 Mark 35
2 Mark 30
8 Lee 40
1 Jorge 19
5 Frank 28
6 Bill 34
4 Bill 16
我的代码
class Util {
public static List<Person> getPersons() {
List<Person> col = new ArrayList<Person>();
col.add(new Person(5, "Frank", 28));
col.add(new Person(1, "Jorge", 19));
col.add(new Person(6, "Bill", 34));
col.add(new Person(3, "Michel", 10));
col.add(new Person(7, "Simpson", 8));
col.add(new Person(4, "Bill",16 ));
col.add(new Person(8, "Lee", 40));
col.add(new Person(9, "Mark", 35));
col.add(new Person(2, "Mark", 30));
return col;
}
}
class Person implements Comparator<Person> {
private int perId;
private String name;
private int age;
public Person(){}
public Person(int perId, String name, int age) {
this.perId = perId;
this.name = name;
this.age = age;
}
//.... getters/setters
@Override
public int compare(Person e1, Person e2) {
return e2.getName().compareTo(e1.getName());
}
}
class PersonId implements Comparable<Person>{
private Integer perId;
@Override
public int compareTo(Person o) {
return this.perId.compareTo(o.getPerId());
}
//...getter
}
public class TestPersonSort {
public static void main(String[] args) {
List<Person> coll = Util.getPersons();
Collections.sort(coll, new Person());
// sort method
printList(coll);
//problem here ***********************************************
//Collections.sort(coll);
}
private static void printList(List<Person> list) {
System.out.println("PerId\tName\tAge");
for (Person e: list) {
System.out.println(e.getPerId() + "\t" + e.getName() + "\t" + e.getAge());
}
}
}
答案 0 :(得分:2)
让Comparator
课程首先比较这个人的姓名。如果比较不是0
,请将其返回。如果是0
,则继续比较此人的年龄。
public int compare(Person e1, Person e2) {
int comp = e2.getName().compareTo(e1.getName()); // desc
if (comp != 0) return comp;
return e1.getAge() - e2.getAge(); // asc
}
另一个更复杂但更灵活的选择是拥有一个使用其他Comparator
的{{1}}。然后,您可以提供Comparator
来比较Comparator<Person>
中的每个属性,以组合它们的效果。
List
答案 1 :(得分:0)
一种简单的方法是Person
实施Comparable<Person>
。然后,main()
可以使用Collections.sort(coll);
class Person implements Comparable<Person> {
private int perId;
private String name;
private int age;
public Person(){}
public Person(int perId, String name, int age) {
this.perId = perId;
this.name = name;
this.age = age;
}
//.... getters/setters
@Override
public int compareTo(Person other) {
int result;
if (other == null)
return(0);
if (other == this)
return(0);
result = name.compareTo(other.name);
if (result != 0)
return(-result); // Sort names in reverse
return(age - other.age); // Sort age ascending
}
}