類按照類中的某一個屬性（或者多個屬性）來對類的物件進行排序，

　　有兩種方法可以實現，

　　1、實現Comparable<T>介面，然後呼叫Collections.sort(List)方法進行排序，

　　2、不實現Comparable<T>介面，而在排序時使用Collections.sort(List, Comparator<T>)方法，並實現其中的Comparator<T>介面。

　　以下，實現一個類的排序

public class Student {
 private String name;
 private int age;
 public
 
 Student() {}
 
 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;
 }
}

一、通過類實現Comparable<T>介面進行排序

public class Student implements Comparable<Student>{
 
 private String name;
 private int age;
 public Student() {}
 
 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;
 }
 
 /**
 * 將物件按姓名字典序升序排序
 * @param o
 * @return
 */
 
 @Override
 
 public int compareTo(Student o) {
 return this.name.compareTo(o.getName());
 }
 
 @Override
 public String toString() {
 return "Student{" +
  "name='" + name + '\'' +
  ", age=" + age +
  '}';
 }
 
}

二、通過在Collections.sort()方法中實現Comparable<T>介面來實現排序

public class Client {
 
 public static void main(String[] args){
 List<Student> students = new ArrayList<>();
 students.add(new Student("a", 18));
 students.add(new Student("c", 19));
 students.add(new Student("b", 20));
 
 Collections.sort(students, new Comparator<Student>() {
  @Override
  public int compare(Student o1, Student o2) {
  return o1.getAge()>o2.getAge()? -1:(o1.getAge()==o2.getAge()? 0:1);
  }
 });
 
 for(Student student:students){
  System.out.println(student.toString());
 }
 }
}