Java 8 Lambda function that throws exception?

In Java 8, you can use a lambda expression to create a functional interface that throws an exception. To do this, you need to use a functional interface that declares the exception in its throws clause, or create your own functional interface that declares the exception.

Here is an example of using a functional interface that declares an exception in its throws clause:

@FunctionalInterface
interface ThrowingFunction {
    R apply(T t) throws E;
}

ThrowingFunction parseInt = s -> Integer.parseInt(s);

try {
    int number = parseInt.apply("123");
} catch (NumberFormatException e) {
    // handle exception
}

In this example, the ThrowingFunction interface is a functional interface that declares a NumberFormatException in its throws clause. The parseInt variable is a lambda expression that calls the Integer.parseInt() method, which can throw a NumberFormatException.

To handle the exception, you need to use a try-catch block around the lambda expression.

You can also create your own functional interface that declares the exception in the throws clause:

@FunctionalInterface
interface MyFunction {
    R apply(T t) throws Exception;
}

MyFunction parseInt = s -> Integer.parseInt(s);

try {
    int number = parseInt.apply("123");
} catch (Exception e) {
    // handle exception
}

In this example, the MyFunction interface is a functional interface that declares an Exception in its throws clause. The parseInt variable is a lambda expression that calls the Integer.parseInt() method, which can throw an Exception.

I hope this helps. Let me know if you have any questions.