java8 中 对list进行排序

对数字进行排序

//对数字进行排序
List<Integer> nums = Arrays.asList(3,1,5,2,9,8,4,10,6,7);
nums.sort(Comparator.reverseOrder()); //reverseOrder倒序
System.err.println("倒序:"+nums);//倒序:[10, 9, 8, 7, 6, 5, 4, 3, 2, 1]

nums.sort(Comparator.naturalOrder());//naturalOrder自然排序即：正序
System.err.println("正序:"+nums);//正序:[1, 2, 3, 4, 5, 6, 7, 8, 9, 10]

 

按照对象进行排序

//按照对象某个属性进行排序：例如年龄
List<User> users = new ArrayList<>();
users.add(new User("u1",22));
users.add(new User("u2",18));
users.add(new User("u3",35));
users.add(new User("u4",16));
users.add(new User("u5",40));

/** * o1,o2表示需要比较的对象， * 正序：o1.getAge().compareTo(o2.getAge()) * 倒序：o2.getAge().compareTo(o1.getAge()) **/
users.sort((o1, o2) -> o1.getAge().compareTo(o2.getAge()));
System.err.println("age正序:"+users);//age正序:[User{name='u4', age=16}, User{name='u2', age=18}, User{name='u1', age=22}, User{name='u3', age=35}, User{name='u5', age=40}]

users.sort((o1, o2) -> o2.getAge().compareTo(o1.getAge()));
System.err.println("age倒序:"+users);//age倒序:[User{name='u5', age=40}, User{name='u3', age=35}, User{name='u1', age=22}, User{name='u2', age=18}, User{name='u4', age=16}]