java自定义排序Comparable<T>和Compartor

代码1

List<Integer> list = Arrays.asList(10,1,3,4,6,7);
        // 降序排列
        Collections.sort(list, new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o2.compareTo(o1);
            }
        });
        for (Integer item : list){
            System.out.println(item);
        }

代码2：

class StudentTest implements Comparable<StudentTest> {
    private String name;
    private int age;

    public StudentTest() {
    }

    public StudentTest(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;
    }

    @Override
    public String toString() {
        return "name:" + this.name + ";age:" + this.age;
    }

    @Override
    public int compareTo(StudentTest o) {
        // 先按age排序
        if (this.age > o.getAge()) {
            return (this.age - o.getAge());
        }
        if (this.age < o.getAge()) {
            return (this.age - o.getAge());
        }

        // 再按name排序
        if (this.name.compareTo(o.getName()) > 0) {
            return 1;
        }
        if (this.name.compareTo(o.getName()) < 0) {
            return -1;
        }
        return 0;
    }
}

使用：

StudentTest[] list = new StudentTest[4];
        list[0] = new StudentTest("b1", 20);
        list[1] = new StudentTest("a2", 50);
        list[2] = new StudentTest("a1", 20);
        list[3] = new StudentTest("b2", 40);
        Arrays.sort(list);
        System.out.println(Arrays.toString(list));

输出：
[name:a1;age:20, name:b1;age:20, name:b2;age:40, name:a2;age:50]
说明：返回值大于0：靠前；等于0：不变；小于零：靠后。
Comparator方式：

Arrays.sort(list,new Comparator<StudentTest>() {
            @Override
            public int compare(StudentTest o1, StudentTest o2) {
                // 先按age倒序排序
                if (o1.getAge() > o2.getAge()) {
                    return -1;
                }
                if (o1.getAge() < o2.getAge()) {
                    return 1;
                }
                // 再按name倒序
                if (o1.getName().compareTo(o2.getName()) > 0) {
                    return -1;
                }
                if (o1.getName().compareTo(o2.getName()) < 0) {
                    return 1;
                }
                return 0;
            }
        });
        System.out.println(Arrays.toString(list));

输出：[name:a2;age:50, name:b2;age:40, name:b1;age:20, name:a1;age:20]