- Java8部分特性及list的常见操作
public class SkuList {
public static void main(String[] args) {
List<User> students = new ArrayList<>();
User st1 = new User();
st1.setId(123);
st1.setAge(10);
User st2 = new User();
st2.setId(789);
st2.setAge(20);
User st3 = new User();
st3.setId(456);
st3.setAge(20);
students.add(st1);
students.add(st2);
students.add(st3);
/* TODO: 输出：list分割：[[{"age":10,"id":123},{"age":20,"id":123}],[{"age":20,"id":456}]]
List<List<User>> splits = Lists.partition(students, 2);
System.out.println("list分割：" + JSON.toJSONString(splits));*/
/* TODO: 输出：list根据年龄进行分组：{20:[{"age":20,"id":123},{"age":20,"id":456}],10:[{"age":10,"id":123}]}
Map<Integer, List<User>> listMap = students.stream().collect(Collectors.groupingBy(User::getAge));
System.out.println("list根据年龄进行分组：" + JSON.toJSONString(listMap));*/
/* TODO: 输出：list转换为Map：{789:{"age":20,"id":789},456:{"age":20,"id":456},123:{"age":10,"id":123}}
Map<Integer, User> userMap = students.stream().collect(Collectors.toMap(User::getId, Function.identity()));
System.out.println("list转换为Map：" + JSON.toJSONString(userMap));*/
/* TODO: 输出：list过滤filter :[{"age":20,"id":789},{"age":20,"id":456}]
List<User> oldStu = students.stream().filter(
student -> student.getAge() > 10).collect(Collectors.toList());
System.out.println("list过滤filter :" + JSON.toJSONString(oldStu));*/
/* TODO: 输出：list对象转化:[{"age":10,"id":123,"title":"教师"},{"age":20,"id":789,"title":"教师"},{"age":20,"id":456,"title":"教师"}]
List<Teacher> teachers = students.stream().map(
student -> {
Teacher teacher = new Teacher();
BeanUtils.copyProperties(student, teacher);
teacher.setTitle("教师");
return teacher;
}).collect(Collectors.toList());
System.out.println("list对象转化:" + JSON.toJSONString(teachers));*/
/* TODO: 输出：list转set：[20, 10]
Set<Integer> ages = students.stream().map(User::getAge).collect(Collectors.toSet());
System.out.println("list转set：" + ages);*/
/* TODO: 输出：[奔驰, 宝马, 奥迪]
List<Customer> customerList = new ArrayList<>();
customerList.add(new Customer(1L, "奔驰"));
customerList.add(new Customer(2L, "宝马"));
customerList.add(new Customer(3L, null));
customerList.add(null);
customerList.add(new Customer(5L, null));
customerList.add(new Customer(6L, "奥迪"));
List<String> nameList1 = customerList.stream()
.filter(Objects::nonNull) // 過濾掉Customer為null的元素
.map(Customer::getName)
.filter(Objects::nonNull) // 過濾掉Customer.getName()為null的元素
.collect(Collectors.toList());
System.out.println(nameList1);*/
}
}
@Data
class User {
private Integer id;
private Integer age;
}
/**
* 转换使用
*/
@Data
class Teacher {
private Integer id;
private Integer age;
private String title;
}
@Data
@AllArgsConstructor
class Customer {
private Long id;
private String name;
}
