public static void main(String[] args) {
        List<User> userList = new ArrayList<>();
        User one = new User();
        one.setId(1);
        one.setAge(2);
        one.setName("haha");

        User two = new User();
        two.setId(10);
        two.setAge(5);
        two.setName("gaga");

        userList.add(one);
        userList.add(two);
		
		//如果满足条件的对象存在
        User user = userList.stream().filter(t -> 1 == t.getId()).findAny().get();
        System.out.println("have: " + user.toString());
		//如果对象不存在，则会抛出异常：java.util.NoSuchElementException: No value present
		User e = userList.stream().filter(t -> 3 == t.getId()).findAny().get();
        System.out.println(e);
        
        //如果对象不存在则返回特定对象
        User n = userList.stream().filter(t -> 3 == t.getId()).findAny().orElse(null);
        System.out.println(n);
		
		//判断对象是否存在
        boolean b = userList.stream().filter(t -> 3 == t.getId()).findAny().isPresent();
        System.out.println("noHaving: " + b);

        



    }

public class User {
    private Integer id;
    private Integer age;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    private String name;

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", age=" + age +
                ", name='" + name + '\'' +
                '}';
    }