How to avoid null checking in Java?

Question

I use object != null a lot to avoid NullPointerException.

Is there a good alternative to this?

For example I often use:

Answer 1

If undefined values are not permitted:

You might configure your IDE to warn you about potential null dereferencing. E.g. in Eclipse, see Preferences > Java > Compiler > Errors/Warnings/Null analysis.

If undefined values are permitted:

If you want to define a new API where undefined values make sense, use the Option Pattern (may be familiar from functional languages). It has the following advantages:

• It is stated explicitly in the API whether an input or output exists or not.
• The compiler forces you to handle the "undefined" case.
• Option is a monad, so there is no need for verbose null checking, just use map/foreach/getOrElse or a similar combinator to safely use the value (example).

Java 8 has a built-in Optional class (recommended); for earlier versions, there are library alternatives, for example Guava's Optional or FunctionalJava's Option. But like many functional-style patterns, using Option in Java (even 8) results in quite some boilerplate, which you can reduce using a less verbose JVM language, e.g. Scala or Xtend.

If you have to deal with an API which might return nulls, you can't do much in Java. Xtend and Groovy have the Elvis operator ?: and the null-safe dereference operator ?., but note that this returns null in case of a null reference, so it just "defers" the proper handling of null.