Java8新特性Lambda表达式的基本使用(常用功能)

Java8新特性Lambda表达式的基本使用

import java.util.Arrays;
import java.util.Comparator;
import java.util.List;
import java.util.function.Predicate;
import java.util.stream.Collectors;

/**
* @Author: Joker·Yang
* @Date: 2018/2/23
* @Desc:
*/
public class LambdaMain {
public static void main(String[] args) {
List<User> users = Arrays.asList(
new User(1, "Joker"), new User(2, "Miller"), new User(3, "David"),
new User(4, "Tony"), new User(5, "Tiger"), new User(6, "Dinggo"),
new User(7, "Lily"), new User(8, "James")
);
print(users);
sort(users, 1);//排序
print(users);
List<String> names = getAllName(users);//获取所有用户名
print(names);
List<User> userList = getUsers(users, (s) -> s.contains("er"));//根据条件筛选
print(userList);
List<User> pageList = pagesUser(users, 1, 3, 4);//排序分页
print(pageList);
doSomething((u) -> System.out.println("用户编号：" + u.getId() + ",用户名：" + u.getName()));//匿名类
}

/**
* 遍历
*/
private static void print(List<? extends Object> objects) {
if (objects != null) objects.forEach(System.out::println);//方式一
//users.forEach((u) -> System.out.println(u));//方式二(当使用此方式编译器会自动提示修改为方式一)
System.out.println("---华丽分割线---");
}

/**
* 升序排序
*/
private static void upSort(List<User> users) {
users.sort(Comparator.comparing(User::getName));
}

/**
* 降序排序
*/
private static void downSort(List<User> users) {
users.sort((User u1, User u2) -> u2.getName().compareTo(u1.getName()));
}

/**
* 排序
*/
private static void sort(List<User> users, int sortType) {
if (sortType == 1) upSort(users);
if (sortType == 2) downSort(users);
}

/**
* 获取姓名集合
*/
private static List<String> getAllName(List<User> users) {
return users.stream().map(User::getName).collect(Collectors.toList());
}

/**
* 按照条件过滤用户
*/
private static List<User> getUsers(List<User> users, Predicate<String> condition) {
return users.stream().filter((u) -> condition.test(u.getName())).collect(Collectors.toList());
}

/**
* 分页
*/
private static List<User> pagesUser(List<User> users, int sortType, int pageSize, int pageIndex) {
sort(users, sortType);
return users.stream().skip((long) (pageIndex - 1) * pageSize).limit((long) pageSize).collect(Collectors.toList());
}
/**
* 匿名类
*/
private static void doSomething(LambdaRun run) {
run.doSomething(new User(99, "Java"));
}
}

/**
* @Author: Joker·Yang
* @Date: 2018/2/23
* @Desc:
*/
@Data
public class User {

public User(Integer id, String name) {
this.id = id;
this.name = name;
}

private Integer id;
private String name;
}

/**
* @Author: Joker·Yang
* @Date: 2018/2/24
* @Desc:
*/
public interface LambdaRun {
void doSomething(User user);
}