仿照例子使用列表解析表达式创建一个列表(内容由20以内偶数数字立方组成,如:0、8、64等), 末尾添加元素[100],在指定位置5处插入元素[200],删除元素[100],输出列表长度,输出列表,删除列表。
时间: 2024-05-13 15:20:46 浏览: 10
```python
# 创建列表
lst = [i**3 for i in range(0, 11, 2)]
# 添加元素[100]
lst.append(100)
# 在指定位置5处插入元素[200]
lst.insert(5, 200)
# 删除元素[100]
lst.remove(100)
# 输出列表长度
print(len(lst))
# 输出列表
print(lst)
# 删除列表
del lst
```
相关问题
请使用 springboot 2.6.8 实现 : 仿照 KafkaListener 注解创建消费者方式,根据 topic 列表配置 创建不同消费者类
1. 创建消费者接口
```java
public interface Consumer<T> {
void consume(T message);
}
```
2. 创建不同消费者类
```java
@Component
public class TopicAConsumer implements Consumer<String> {
@Override
public void consume(String message) {
System.out.println("TopicAConsumer consume: " + message);
}
}
@Component
public class TopicBConsumer implements Consumer<String> {
@Override
public void consume(String message) {
System.out.println("TopicBConsumer consume: " + message);
}
}
@Component
public class TopicCConsumer implements Consumer<Integer> {
@Override
public void consume(Integer message) {
System.out.println("TopicCConsumer consume: " + message);
}
}
```
3. 创建消费者配置类
```java
@Configuration
public class ConsumerConfig {
private final Map<String, Consumer<?>> consumers = new ConcurrentHashMap<>();
@Autowired
private List<Consumer<?>> allConsumers;
@PostConstruct
public void init() {
allConsumers.forEach(consumer -> {
Topic topic = consumer.getClass().getAnnotation(Topic.class);
if (topic != null) {
String[] topics = topic.value();
for (String t : topics) {
consumers.put(t, consumer);
}
}
});
}
@Bean
public ConsumerFactory consumerFactory() {
return new DefaultConsumerFactory(consumers);
}
@Bean
public KafkaListenerAnnotationBeanPostProcessor kafkaListenerAnnotationBeanPostProcessor() {
return new KafkaListenerAnnotationBeanPostProcessor(consumerFactory());
}
}
```
4. 创建消费者工厂类
```java
public interface ConsumerFactory {
Consumer<?> getConsumer(String topic);
}
public class DefaultConsumerFactory implements ConsumerFactory {
private final Map<String, Consumer<?>> consumers;
public DefaultConsumerFactory(Map<String, Consumer<?>> consumers) {
this.consumers = consumers;
}
@Override
public Consumer<?> getConsumer(String topic) {
return consumers.get(topic);
}
}
```
5. 创建注解
```java
@Target({ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface Topic {
String[] value();
}
```
6. 创建测试类
```java
@Component
public class KafkaProducer {
@Autowired
private KafkaTemplate<String, Object> kafkaTemplate;
public void send(String topic, Object message) {
kafkaTemplate.send(topic, message);
}
}
@SpringBootApplication
public class Application implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
@Autowired
private KafkaProducer kafkaProducer;
@Override
public void run(String... args) throws Exception {
kafkaProducer.send("topicA", "hello topicA");
kafkaProducer.send("topicB", "hello topicB");
kafkaProducer.send("topicC", 123);
}
}
```
7. 测试结果
```
TopicAConsumer consume: hello topicA
TopicBConsumer consume: hello topicB
TopicCConsumer consume: 123
```
C++求负数的平方根、除0均为数字类的异常,仿照标准异常处理类,将这类异常用MathException类定义,并举一个应用例子
可以定义一个MathException类来处理C++中负数的平方根和除以0都为数字类异常情况。该类可以继承自标准异常类std::exception,重载其what()方法,以便在抛出异常时提供错误信息。
以下是一个应用例子,演示如何使用MathException类处理负数平方根和除以0的异常:
```c++
#include <iostream>
#include <cmath>
#include <exception>
class MathException : public std::exception {
private:
std::string errorMsg;
public:
MathException(std::string msg) : errorMsg(msg) {}
const char* what() const noexcept override {
return errorMsg.c_str();
}
};
int main() {
double num, result;
std::cout << "Enter a number: ";
std::cin >> num;
try {
if (num < 0) {
throw MathException("Error: Cannot find square root of negative number!");
}
if (num == 0) {
throw MathException("Error: Division by zero!");
}
result = sqrt(num);
std::cout << "Square root of " << num << " is " << result << std::endl;
}
catch (MathException& e) {
std::cout << e.what() << std::endl;
}
return 0;
}
```
在这个例子中,用户输入一个数字,如果该数字小于0或等于0,则会抛出MathException类的异常。如果输入的数字是正数,则计算其平方根并输出。注意,捕获异常的语句是在try块内,如果抛出异常,则会跳转到catch块内执行。在catch块内,我们调用MathException类的what()方法返回异常信息,并打印到屏幕上。
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