34.Collections

        ArrayList<String> strings = new ArrayList<String>();
        strings.add("aa");
        strings.add("dd");
        strings.add("cc");
        strings.add("ee");
        System.out.println(strings);
        Collections.sort(strings);
        System.out.println(strings);
        Collections.reverse(strings);
        System.out.println(strings);
        Collections.shuffle(strings);
        System.out.println(strings);

[aa, dd, cc, ee]
[aa, cc, dd, ee]
[ee, dd, cc, aa]
[cc, ee, aa, dd]

    public static void main(String[] args) {
        ArrayList<Student> students = new ArrayList<Student>();
        Student student1 = new Student("张三", 18);
        Student student2 = new Student("李四", 19);
        Student student3 = new Student("王二", 29);
        Student student4 = new Student("麻子", 17);
        Student student5 = new Student("赵柳", 26);
        students.add(student1);
        students.add(student2);
        students.add(student3);
        students.add(student4);
        students.add(student5);
        Collections.sort(students, new Comparator<Student>() {
            @Override
            public int compare(Student s1, Student s2) {
                int ageRet = s1.getAge() - s2.getAge();
                int resault = ageRet == 0 ? s1.getName().compareTo(s2.getName()) : ageRet;
                return resault;
            }
        });
        for (Student s : students) {
            System.out.println(s);
        }
    }