Java Exceptions in Lambda

In Java, a lambda expression is a concise way to represent a function as an object. Lambdas are used to define functional interfaces, which are interfaces with a single abstract method.

Like any other code in Java, lambda expressions can throw exceptions. However, the types of exceptions that can be thrown by a lambda expression are restricted by the functional interface that the lambda is implementing.

Here is an example of a lambda expression that throws an exception:

import java.io.IOException;

@FunctionalInterface
interface Lambda {
    void run() throws IOException;
}

public class Main {
    public static void main(String[] args) {
        Lambda lambda = () -> {
            throw new IOException("I/O error occurred.");
        };

        try {
            lambda.run();
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
    }
}

In this example, the Lambda interface is a functional interface with a single abstract method called run that can throw an IOException. The lambda expression () -> { throw new IOException("I/O error occurred."); } implements the run method and throws an IOException when it is called. The try-catch block is used to handle the exception.

Note that the exception types that can be thrown by a lambda expression are determined by the functional interface that the lambda is implementing. In this case, the run method of the Lambda interface is declared to throw an IOException, so the lambda expression is allowed to throw an IOException. If the run method did not declare that it could throw an exception, the lambda expression would not be allowed to throw an exception.