list對象排序

public class Student { private int studentId; private String studentName; private int age; private String upDate;

public Student(int studentId, String studentName, int age, String date) {
    this.studentId = studentId;
    this.studentName = studentName;
    this.age = age;
    this.upDate = date;
}

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;
}

public String getUpDate() {
    return upDate;
}

public void setUpDate(String upDate) {
    this.upDate = upDate;
}

第一種：實例化一個比較器

public class test {

public static void main(String[] args) {
    Comparator<Student> comparator = new Comparator<Student>() {
        public int compare(Student s1, Student s2) {
            // 排序：更新時間 -- 年齡 --姓名---學號
            SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
            try {
                Date dt1 = format.parse(s1.getUpDate());
                Date dt2 = format.parse(s2.getUpDate());
                if (dt1.getTime() != dt2.getTime()) {
                    if (dt1.getTime() > dt2.getTime()) {
                        return 1;
                    }
                }
                else if (s1.getAge() != s2.getAge()) {
                    return s1.getAge() - s2.getAge();
                } else if (!s1.getStudentName().equals(s2.getStudentName())) {
                    return s1.getStudentName().compareTo(s2.getStudentName());
                } else {
                    return s1.getStudentId() - s2.getStudentId();
                }
            } catch (ParseException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
            return 0;
        }
    };
    Student stu1 = new Student(1, "zhangsan", 28, "2017-11-01");
    Student stu2 = new Student(2, "zhagnsan", 19, "2017-11-01");
    Student stu3 = new Student(3, "wangwu", 19, "2017-11-02");
    Student stu4 = new Student(4, "wangwu", 19, "2017-12-02");
    Student stu5 = new Student(5, "zhaoliu", 18, "2017-12-08");

    ArrayList<Student> list = new ArrayList<Student>();
    list.add(stu1);
    list.add(stu2);
    list.add(stu3);
    list.add(stu4);
    list.add(stu5);
    // 這裏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("更新時間：" + stu.getUpDate() + " 年齡:" + stu.getAge() + "   姓名:" + stu.getStudentName() + "   學號:" + stu.getStudentId());
    }
}

}

第二種：實現Comparable 接口

public class Student2 implements Comparable<Student2> { private int studentId; private String studentName; private int age; private String upDate;

public Student2(int studentId, String studentName, int age, String date) {
    this.studentId = studentId;
    this.studentName = studentName;
    this.age = age;
    this.upDate = date;
}

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;
}

public String getUpDate() {
    return upDate;
}

public void setUpDate(String upDate) {
    this.upDate = upDate;
}

[@Override](https://my.oschina.net/u/1162528)
public int hashCode() {
    return 0;
}

[@Override](https://my.oschina.net/u/1162528)
public boolean equals(Object obj) {
    if (obj instanceof Student2) {
        Student2 stu = (Student2) obj;
        if ((age == stu.getAge()) && (studentName.equals(stu.getStudentName())) && (studentId == stu.getStudentId())) {
            return true;
        } else
            return true;
    } else {
        return false;
    }
}

[@Override](https://my.oschina.net/u/1162528)
public int compareTo(Student2 o) {
    SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
    Date dt1;
    try {
        dt1 = format.parse(o.getUpDate());
        Date dt2 = format.parse(upDate);
        if (dt1.getTime() != dt2.getTime()) {
            if (dt1.getTime() > dt2.getTime()) {
                return 1;
            }
        } else if (age != o.getAge()) {
            return age - o.getAge();
        } else if (!studentName.equals(o.getStudentName())) {
            return studentName.compareTo(o.getStudentName());
        } else {
            return studentId - o.getStudentId();
        }
    } catch (ParseException e) {
        e.printStackTrace();
    }
    return 0;
}

}

public class test2 { /** * @param args */ public static void main(String[] args) { Student2 stu1 = new Student2(1, "zhangsan", 28, "2017-11-01"); Student2 stu2 = new Student2(2, "zhagnsan", 19, "2017-11-01"); Student2 stu3 = new Student2(3, "wangwu", 19, "2017-11-02"); Student2 stu4 = new Student2(4, "wangwu", 19, "2017-12-02"); Student2 stu5 = new Student2(5, "zhaoliu", 18, "2017-12-08");

ArrayList<Student2> list = new ArrayList<Student2>();
    list.add(stu1);
    list.add(stu2);
    list.add(stu3);
    list.add(stu4);
    list.add(stu5);
    // 這裏就會自動根據規則進行排序
    Collections.sort(list);
    for (int i = 0; i < list.size(); i++) {
        Student2 stu = list.get(i);
        System.out.println("更新時間："+stu.getUpDate()+ " 年齡:" + stu.getAge() + "   姓名:" + stu.getStudentName() + "   學號:" + stu.getStudentId());
    }

}

}

第三種：補充說明SortList，可做爲擴展

public class SortList<E> {

@SuppressWarnings({"unchecked", "rawtypes"})
public void Sort(List<E> list, final String method, final String
                sort) {
    Collections.sort(list, new Comparator() {
        public int compare(Object a, Object b) {
            int ret = 0;
            try {
                Method m1 = ((E) a).getClass().getMethod(method, null);
                Method m2 = ((E) b).getClass().getMethod(method, null);
                if (sort != null && "desc".equals(sort)) // 倒序
                    ret = m2.invoke(((E) b), null).toString().compareTo(m1.invoke(((E) a), null).toString());
                else
                    // 正序
                    ret = m1.invoke(((E) a), null).toString().compareTo(m2.invoke(((E) b), null).toString());
            } catch (Exception ne) {
                System.out.println(ne);
            }
            return ret;
        }
    });
}

}

public class test {

public static void main(String[] args) {
    
    Student stu1 = new Student(1, "zhangsan", 28, "2017-11-01");
    Student stu2 = new Student(2, "zhagnsan", 19, "2017-11-01");
    Student stu3 = new Student(3, "wangwu", 19, "2017-11-02");
    Student stu4 = new Student(4, "wangwu", 19, "2017-12-02");
    Student stu5 = new Student(5, "zhaoliu", 18, "2017-12-08");

    ArrayList<Student> list = new ArrayList<Student>();
    list.add(stu1);
    list.add(stu2);
    list.add(stu3);
    list.add(stu4);
    list.add(stu5);

    SortList<Student> sortList = new SortList<Student>();
    //可擴展成數組
    sortList.Sort(list, "getUpDate", "asc");
    for (int i = 0; i < list.size(); i++) {
        Student stu = list.get(i);
        System.out.println("更新時間：" + stu.getUpDate() + " 年齡:" + stu.getAge() + "   姓名:" + stu.getStudentName() + "   學號:" + stu.getStudentId());
    }

}

}