1. 首先聲明一個函數式接口，就只接口內只有一個抽象方法

//函數式接口
public interface Factory {Object getObject();}

2. 接口實現類

public class SubClass implements Factory {@Overridepublic Object getObject() {return new User();}}

3. User類

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

4. 測試類：

public class LambdaTest {public static void main(String[] args) {//1.子類實現接口Factory factory = new SubClass();User user = (User)factory.getObject();System.out.println(user);//2.匿名內部類factory = new Factory() {@Overridepublic Object getObject() {return new User("zhangsan",33);}};User object = (User)factory.getObject();System.out.println(object);//3.lambda表達式factory = () -> {return new User("李斯特",33);};Object object1 = factory.getObject();System.out.println(object1.toString());System.out.println("-----------------------------------------");//4.使用lambda表達式，做為參數傳遞User user4 = getUserFromFactory(() -> {return new User("wangwuxxx", 223);}, "User");System.out.println(user4);System.out.println("-----------------------------------------");//5. 使用lambda做為返回值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); };}
}