EC
NoSuchElementException
JavaERRORCommonCollection

No element available in iterator or Optional

Quick Answer

Check hasNext() before next(), or use Optional.orElse() instead of Optional.get().

What this means

Thrown by Iterator.next(), Scanner methods, or Optional.get() when no element is available.

Why it happens
  1. 1Calling Iterator.next() without checking hasNext()
  2. 2Optional.get() on an empty Optional

Fix

Use orElse / orElseThrow instead of get

Use orElse / orElseThrow instead of get
String val = opt.orElse("default");
String val2 = opt.orElseThrow(
    () -> new IllegalStateException("value required"));

Why this works

orElseThrow gives a more descriptive error than NoSuchElementException from get().

Code examples
Triggerjava
Optional.empty().get(); // NoSuchElementException
Safe Optionaljava
String result = findUser(id)
    .map(User::getName)
    .orElse("unknown");
Stream findFirstjava
list.stream()
    .filter(s -> s.startsWith("A"))
    .findFirst()
    .orElseThrow(() -> new NotFoundException("no match"));
Sources
Official documentation ↗

Java SE Documentation

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