Author: limpbizkit
Date: Thu Jan 1 13:51:48 2009
New Revision: 770
Added:
wiki/UseNullable.wiki
Log:
Created wiki page through web user interface.
Added: wiki/UseNullable.wiki
==============================================================================
--- (empty file)
+++ wiki/UseNullable.wiki Thu Jan 1 13:51:48 2009
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+=Use @Nullable=
+To eliminate `NullPointerExceptions` in your codebase, you must be
disciplined about null references. We've been successful at this by
following and enforcing a simple rule:
+ _Every parameter is non-null unless explicitly specified._
+The [http://code.google.com/p/google-collections/ Google Collections
library] has simple APIs to get a nulls under control.
`Preconditions.checkNotNull` can be used to fast-fail if a null reference
is found, and `...@nullable` can be used to annotate a parameter that permits
the `null` value:
+{{{
+import static com.google.common.base.Nullable;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+public class Person {
+ ...
+
+ public Person(String firstName, String lastName, @Nullable Phone phone) {
+ this.firstName = checkNotNull(firstName, "firstName");
+ this.lastName = checkNotNull(lastName, "lastName");
+ this.phone = phone;
+ }
+}}}
+*Guice forbids null by default.* It will refuse to inject `null`, failing
with a `ProvisionException` instead. If `null` is permissible by your
class, you can annotate the field or parameter with `...@nullable`. Guice
recognizes any `...@nullable` annotation, like
[http://google-collections.googlecode.com/svn/trunk/javadoc/com/google/common/base/Nullable.html
com.google.common.base.Nullable] or
[http://code.google.com/p/jsr-305/source/browse/trunk/ri/src/main/java/javax/annotation/Nullable.java?r=24
javax.annotation.Nullable].
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