在Android開發中，有時我們需要對一個物件的集合按照某一個欄位進行排序，

• Bean

public class Student {
    private int studentId;
    private String studentName;
    private int age;
    public Student(int studentId , String studentName, int age){
        this.studentId=studentId;
        this.studentName=studentName;
        this
 
.age=age;
    }
    public int getStudentId() {
        return studentId;
    }
    public void setStudentId(int studentId) {
        this.studentId = studentId;
    }
    public String getStudentName() {
        return studentName;
    }
    public void setStudentName(String studentName) {
        this
 
.studentName = studentName;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }

}

• 實現排序

  實現排序比較類 Comparator ，裡面實現排序規則。

public class test {

    /**
     * @param args
     */
    public static void main(String[] args) {
         Student stu1 = new
 
 Student (1,"zhangsan",28);
         Student stu2 = new Student (2,"zhagnsan",19);
         Student stu3 = new Student (3,"wangwu",19);
         Student stu4 = new Student (4,"wangwu",19);
         Student stu5 = new Student (5,"zhaoliu",18);

          ArrayList<Student> list = new ArrayList<Student>();
          list.add(stu1);
          list.add(stu2);
          list.add(stu3);
          list.add(stu4);
          list.add(stu5); 
//排序規則，這裡是以年齡先排序，如果年齡相同
        Comparator<Student> comparator = new Comparator<Student>() {
            public int compare(Student s1, Student s2) {
                // 先排年齡
                if (s1.getAge() != s2.getAge()) {
                    return s1.getAge() - s2.getAge();
                } else if (!s1.getStudentName().equals(s2.getStudentName())) {
                    // 年齡相同則按姓名排序
                    return s1.getStudentName().compareTo(s2.getStudentName());
                } else {
                    // 姓名也相同則按學號排序
                    return s1.getStudentId() - s2.getStudentId();
                }
            }
        };

          //這裡就會自動根據規則進行排序
          Collections.sort(list,comparator);
          for(int i=0;i<list.size();i++){
              Student stu=list.get(i);
              System.out.println("年齡:"+stu.getAge()+"   姓名:"+stu.getStudentName()+"   學號:"+stu.getStudentId());
          }

    }

}

排序結果

結果：
年齡:18   姓名:zhaoliu   學號:5
年齡:19   姓名:wangwu   學號:3
年齡:19   姓名:wangwu   學號:4
年齡:19   姓名:zhagnsan   學號:2
年齡:28   姓名:zhangsan   學號:1

也可以想下面這樣寫：

    Collections.sort(list, new Comparator<GoodsBean>() {
            @Override
            public int compare(GoodsBean bean1, GoodsBean bean2) {

                if (Integer.valueOf(bean1.getScore()).compareTo(Integer.valueOf(bean2.getScore())) == 0) {
                    return Integer.valueOf(bean1.getRecommend_num()).compareTo(Integer.valueOf(bean2.getRecommend_num()));
                } else {
                    return Integer.valueOf(bean1.getScore()).compareTo(Integer.valueOf(bean2.getScore()));
                }
            }
        });

這樣就可以對一個集合中的資料各種排序了。