Unguarded first element access (ARCH4078)

Key java.performance.first-or-default-null · Severity warning · Category performance

Accessing the first element of a filtered result without an empty check throws when the result is empty. The Optional from findFirst should be handled safely.

Incorrect

User admin = users.stream()
    .filter(User::isAdmin)
    .collect(toList())
    .get(0);
return admin.getName();

Correct

return users.stream()
    .filter(User::isAdmin)
    .findFirst()
    .map(User::getName)
    .orElse("none");

Fix

Use findFirst() instead of get(0) and resolve the returned Optional with orElse.