Java 8可选如何定义NullPointerException的错误消息

Question

Before Java 8, we normally have to do like the following to fail fast for Null values.

Objects.requireNonNull(pointer, "Your Error Message");

According to Java 8 Documentation, Optional.of will throw NullPointerException if passed parameter is null.

// Optional.of - throws NullPointerException if passed parameter is null
Optional<Integer> b = Optional.of(value2);

Is there any way to define error message for NullPointerException in Java 8 Optional ?

Answer 1

你总是可以编写Optional.of(Objects.requireNonNull(pointer, "message")) 。

Answer 2

For the Optional class, you're usually expected to not deal with throwing any errors until the value is extracted. You can use orElseThrow when you try to retrieve the value:

Optional.ofNullable(pointer)
        ...
        ...
        .orElseThrow(() -> new NullPointerException("message"));

The Optional class isn't meant to replace the existing methods for doing specific null-checking.