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What it looks like

java.util.NoSuchElementException: No value present

Extends RuntimeException in java.util.

What it means

It is thrown when you ask for something that is not there: Optional.get() on an empty Optional ("No value present"), Iterator.next() after the last element, Scanner.nextLine() with no more input, Deque.getFirst() or List.getFirst() on an empty collection, and stream.reduce(...).get() on an empty stream.

Common causes

• Calling Optional.get() without checking isPresent().
• Reading more tokens from a Scanner than the input has.
• Calling iterator.next() without hasNext().
• Taking the first element of an empty collection, for example after a filter removed everything.

How to fix it

1. Use orElse, orElseGet or orElseThrow(() -> new MyException(...)) instead of get().
2. Check hasNext() before next(), or use for-each.
3. Check isEmpty() before taking the first or last element, or use peek and poll variants that return null.
4. When absence is a legitimate business case, model it explicitly and return a result type rather than throwing.

Broken and fixed

User u = repo.findById(id).get(); // No value present

User u = repo.findById(id)
        .orElseThrow(() -> new UserNotFoundException(id));

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In Spring and enterprise code

Spring Data repositories return Optional from findById. Throwing a domain exception with the id in the message is far easier to debug than "No value present".

Debug it faster

Paste the whole stack trace into the stack trace beautifier to hide framework frames, jump to the root cause and find the first line of your own code. It runs in your browser, so the trace never leaves your machine.

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