NullPointerException in Java: Unexpected crash at runtime

My code throws a NullPointerException when invoking .equals(...) or calling methods on seemingly non-null objects. How can I prevent this?

This error arises when invoking methods or accessing fields on variables that have null references. Common mistakes and fixes: 🔍 Common Mistakes • Calling s.equals(...) when s is null → produces NPE Wikipediajenkov.comReddit+2GeeksforGeeks+2Medium+2 • Forgetting to initialize variables or missing API null checks 🛠️ Preventive Measures • Call equals on literals: "constant".equals(variable) avoids NPE even if variable is nullGeeksforGeeks • Use annotations like @NonNull/@Nullable combined with tools like NullAway or Checker Framework to enforce null contracts at compile timeReddit • Prefer Java Optional<T> for return values or processing pipelines • Adopt Null Object Pattern—design objects representing the absent case rather than using null