java中的ArrayList需要通过collections类的sort方法来进行排序
如果想自定义排序方式则需要有类来实现Comparator接口并重写compare方法
调用sort方法时将ArrayList对象与实现Commparator接口的类的对象作为参数
示例:
// 外部类的方式
import java.util.ArrayList; import java.util.Collections;
import java.util.Comparator; import java.util.List;
public class Test { public static void main(String[] args) {
Student zlj = new Student("丁晓宇", 21);
Student dxy = new Student("赵四", 22);
Student cjc = new Student("张三", 11);
Student lgc = new Student("刘武", 19);
List<Student> studentList = new ArrayList<Student>();
studentList.add(zlj);
studentList.add(dxy);
studentList.add(cjc);
studentList.add(lgc);
Collections.sort(studentList, new SortByAge());
for (Student student : studentList) {
System.out.println(student.getName() + " / " + student.getAge());
}
System.out.println(" = ");
Collections.sort(studentList, new SortByName());
for (Student student : studentList) {
System.out.println(student.getName() + " / " + student.getAge());
} } }
class SortByAge implements Comparator {
public int compare(Object o1, Object o2) {
Student s1 = (Student) o1; Student s2 = (Student) o2;
if (s1.getAge() > s2.getAge()) return 1; return 0; } }
class SortByName implements Comparator {
public int compare(Object o1, Object o2) {
Student s1 = (Student) o1;
Student s2 = (Student) o2;
return s1.getName().compareTo(s2.getName()); } }
//匿名内部类的方式
//按照受益人级别进行排序
Collections.sort(beneficiarys,new Comparator(){
@Override
public int compare(Object o1, Object o2) {
Beneficiary s1 = (Beneficiary) o1;
Beneficiary s2 = (Beneficiary) o2;
if (Integer.parseInt(s1.getBeneficiaryOrder()) > Integer.parseInt(s2.getBeneficiaryOrder()))
return 1;
return 0;
} });