1. 首先声明一个函数式接口，就只接口内只有一个抽象方法

//函数式接口
public interface Factory {

    Object getObject();

}

2. 接口实现类

public class SubClass implements Factory {

    @Override
    public Object getObject() {
        return new User();
    }

}

3. User类

public class User {

    private String name;
    private int age;

    public User() {
    }

    public User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() {
        return name;
    }

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

    public int getAge() {
        return age;
    }

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

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

4. 测试类：

public class LambdaTest {
    public static void main(String[] args) {

        //1.子类实现接口
        Factory factory = new SubClass();
        User user = (User)factory.getObject();
        System.out.println(user);

        //2.匿名内部类
        factory = new Factory() {
            @Override
            public Object getObject() {
                return new User("zhangsan",33);
            }
        };
        User object = (User)factory.getObject();
        System.out.println(object);

        //3.lambda表达式
        factory = () -> {
            return new User("李斯特",33);
        };
        Object object1 = factory.getObject();
        System.out.println(object1.toString());
        System.out.println("-----------------------------------------");

        //4.使用lambda表达式，做为参数传递
        User user4 = getUserFromFactory(() -> {return new User("wangwuxxx", 223);}, "User");
        System.out.println(user4);

        System.out.println("-----------------------------------------");

        //5. 使用lambda做为返回值
        User user5 = (User)getFactory().getObject();
        System.out.println(user5);
    }


    public static User getUserFromFactory(Factory factory,String beanName){
        Object obj = factory.getObject();
        if(obj != null && obj.getClass().getSimpleName().equals(beanName)){
            return (User) obj;
        }
        return null;
    }

    public static Factory getFactory(){
        return () -> { return new User("dingxx",33); };
    }
}