一、简要描述
- Lambda初体验
- Lambda表达式的语法格式
- Lambda表达式应用举例
- Lambda表达式底层实现
二、什么是Lambda表达式
Java8新特性，来源于数学中的λ[læ:mdə]演算
是一套关于函数(f(x))定义、输入量、输出量的计算方案
- Lambda表达式 -> 函数
- 使代码变得简洁、紧凑
- 函数式编程：
- 函数是“第一等公民”
- 可以作为(其他函数的)返回值
- 可以作为(其他函数的)参数进行传递
- 可以赋值给变量
三、代码实现
1、定义User类
package tech.flygo.lambda.demo1;/*** @description: 用户类* @author: flygo* @time: 2023/5/7 22:59*/
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 + '}';}
}
2、定义Factory接口
package tech.flygo.lambda.demo1;/*** @description: 工程接口* @author: flygo* @time: 2023/5/7 22:58*/
public interface Factory {Object getObject();
}
3、定义Factory接口实现类SubClass
package tech.flygo.lambda.demo1;/*** @description: 接口实现类* @author: flygo* @time: 2023/5/7 22:59*/
public class SubClass implements Factory {@Overridepublic Object getObject() {return new User();}
}
4、定义LambdaTest测试类
package tech.flygo.lambda.demo1;/*** @description: Lambda测试类* @author: flygo* @time: 2023/5/7 23:01*/
public class LambdaTest {public static void main(String[] args) {// 1、子类实现接口Factory factory = new SubClass(); // 多态User user1 = (User) factory.getObject();System.out.println(user1);// 2、匿名内部类factory =new Factory() {@Overridepublic Object getObject() {return new User("张三", 18);}};User user2 = (User) factory.getObject();System.out.println(user2);// 3、Lambda表达式factory =() -> {return new User("李四", 20);};User user3 = (User) factory.getObject();System.out.println(user3);// 4、Lambda作为参数进行传递User user4 =getUserFromFactory(() -> {return new User("王五", 22);},User.class.getSimpleName());System.out.println(user4);// 5、Lambda作为函数返回值factory = getFactory();System.out.println(factory.getObject());}public static User getUserFromFactory(Factory factory, String beanName) {Object object = factory.getObject();if (object != null && object.getClass().getSimpleName().equals(beanName)) {return (User) object;}return null;}public static Factory getFactory() {return () -> {return new User("赵六", 24);};}
}
5、核心代码块
5.1、核心代码块-Lambda表达式
// 3、Lambda表达式
factory =() -> {return new User("李四", 20);};
User user3 = (User) factory.getObject();
System.out.println(user3);5.2、核心代码块-Lambda作为参数进行传递
// 4、Lambda作为参数进行传递
User user4 =getUserFromFactory(() -> {return new User("王五", 22);},User.class.getSimpleName());
System.out.println(user4);......public static User getUserFromFactory(Factory factory, String beanName) {Object object = factory.getObject();if (object != null && object.getClass().getSimpleName().equals(beanName)) {return (User) object;}return null;
}5.3、核心代码块-Lambda作为函数返回值
// 5、Lambda作为函数返回值
factory = getFactory();
System.out.println(factory.getObject());......public static Factory getFactory() {return () -> {return new User("赵六", 24);};
}
