Lambda表达式-实际应该用-实例

List<User> list = new ArrayList<>();
User user1 = new User("张三",15,"男");
User user2 = new User("李四",22,"男");
User user3 = new User("王五",25,"男");
User user4 = new User("赵六",30,"男");
User user5 = new User("李世民",28,"男");
User user6 = new User("杨贵妃",18,"女");
User user7 = new User("貂蝉",16,"女");
list.add(user1);
list.add(user2);
list.add(user3);
list.add(user4);
list.add(user5);
list.add(user6);

//1、单一条件过滤：根据对象中的一个条件过滤（过滤名字不为张三的所有人）
List<User> collect = list.stream().filter(user -> !"张三".equals(user.getName())).collect(Collectors.toList());

//2、多条件过滤：根据对象中的多个属性过滤（过滤，只剩年龄在30岁以下，并且性别为女的用户）
List<User> collect = list.stream().filter(user -> user.getAge()<30 && "女".equals(user.getSex())).collect(Collectors.toList());

List<Emp> filterSalEmp = empService.filter1(listEmp, Emp emp -> emp.getSal() > 3000);
List<Emp> filterJobEmp = empService.filter1(listEmp, Emp emp -> "SALMAN".equals(emp.getJob()));

//3、找到一个班里数学分数高于90分的。
List<Student> newList = list.stream().filter(item -> item.getScore() > 90).collect(Collectors.toList());
//4、找到第一个分数高于90分的。
Optional<Student> optionalStudent = list.stream().filter(item -> item.getScore() > 90).findFirst();

List features = Arrays.asList("Lambdas", "Default Method", "Stream API", "Date and Time API");
        features.forEach(n ->{
             System.out.println(n);
        });
        
//5、获取数字的个数、最小值、最大值、总和以及平均值
List<Integer> primes = Arrays.asList(2, 3, 5, 7, 11, 13, 17, 19, 23, 29);
IntSummaryStatistics stats = primes.stream().mapToInt((x) -> x).summaryStatistics();
System.out.println("Highest prime number in List : " + stats.getMax());
System.out.println("Lowest prime number in List : " + stats.getMin());
System.out.println("Sum of all prime numbers : " + stats.getSum());
System.out.println("Average of all prime numbers : " + stats.getAverage());

6、list

List<User> list = new ArrayList<User>();
        User user1 = new User("第一位","用户1");
        list.add(user1);
        User user2 = new User("第二位","用户2");
        list.add(user2);
        User user3 = new User("第三位","用户3");
        list.add(user3);
        List<String> tableNames=list.stream().map(User::getMessage).collect(Collectors.toList());
        System.out.println("输出第一个："+tableNames);
        List<String> orders=list.stream().map(User::getOrder).collect(Collectors.toList());
        System.out.println(orders)