Avoid NoSuchElementException with Stream

I have the following Stream:

Stream<T> stream = stream();

T result = stream.filter(t -> {
    double x = getX(t);
    double y = getY(t);
    return (x == tx && y == ty);
}).findFirst().get();

return result;

However, there is not always a result which gives me the following error:

>NoSuchElementException: No value present

So how can I return a null if there is no value present?

You can use Optional.orElse, it's much simpler than checking isPresent:

T result = stream.filter(t -> {
    double x = getX(t);
    double y = getY(t);
    return (x == tx && y == ty);
}).findFirst().orElse(null);

return result;

Stream#findFirst() returns an Optional which exists specifically so that you don't need to operate on null values.

> A container object which may or may not contain a non-null value. If a > value is present, isPresent() will return true and get() will return > the value.

Otherwise, Optional#get() throws a NoSuchElementException.

> If a value is present in this Optional, returns the value, otherwise > throws NoSuchElementException.

An Optional will never expose its value if it is null.

If you really have to, just check isPresent() and return null yourself.

Stream<T> stream = stream();

Optional<T> result = stream.filter(t -> {
    double x = getX(t);
    double y = getY(t);
    return (x == tx && y == ty);
}).findFirst();

if (result.isPresent()) 
    return result.get();
return null;

An alternate method for replacing the Optional.get (which more likely than not fails the user's intentions with a NoSuchElementException) is with a more verbose API introduced in JDK10 termed as Optional.orElseThrow(). In author's words -

> Optional.get() is an "attractive nuisance" and is too tempting for > programmers, leading to frequent errors. People don't expect a getter > to throw an exception. A replacement API for Optional.get() with > equivalent semantics should be added.

Note :- The underlying implementation of both these APIs is same, yet the latter reads out more clearly that a NoSuchElementException would be thrown by default if the value is not present which inlines to the existing Optional.orElseThrow​(Supplier<? extends X> exceptionSupplier) implementation used by consumers as an explicit alternate.

If you wish to continue using the object and not throw any exception, then

Optional.isPresent(object) is the way to go