java中对ArrayList进行排序

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:

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());
 }
}