Import jsr305 and use it to mark @Nullable stuff. (#297)

examples/pom.xml

@@ -12,6 +12,11 @@
   <artifactId>moshi-examples</artifactId>
 
   <dependencies>
+    <dependency>
+      <groupId>com.google.code.findbugs</groupId>
+      <artifactId>jsr305</artifactId>
+      <scope>provided</scope>
+    </dependency>
     <dependency>
       <groupId>com.squareup.moshi</groupId>
       <artifactId>moshi</artifactId>

examples/src/main/java/com/squareup/moshi/recipes/DefaultOnDataMismatchAdapter.java

@@ -24,6 +24,7 @@ import java.io.IOException;
 import java.lang.annotation.Annotation;
 import java.lang.reflect.Type;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 public final class DefaultOnDataMismatchAdapter<T> extends JsonAdapter<T> {
   private final JsonAdapter<T> delegate;
@@ -54,7 +55,7 @@ public final class DefaultOnDataMismatchAdapter<T> extends JsonAdapter<T> {
 
   public static <T> Factory newFactory(final Class<T> type, final T defaultValue) {
     return new Factory() {
-      @Override public JsonAdapter<?> create(
+      @Override public @Nullable JsonAdapter<?> create(
           Type requestedType, Set<? extends Annotation> annotations, Moshi moshi) {
         if (type != requestedType) return null;
         JsonAdapter<T> delegate = moshi.nextAdapter(this, type, annotations);

examples/src/main/java/com/squareup/moshi/recipes/Unwrap.java

@@ -28,6 +28,7 @@ import java.lang.annotation.Annotation;
 import java.lang.annotation.Retention;
 import java.lang.reflect.Type;
 import java.util.Set;
+import javax.annotation.Nullable;
 
 import static java.lang.annotation.RetentionPolicy.RUNTIME;
 
@@ -51,8 +52,8 @@ final class Unwrap {
 
   public static final class EnvelopeJsonAdapter extends JsonAdapter<Object> {
     public static final JsonAdapter.Factory FACTORY = new Factory() {
-      @Override
-      public JsonAdapter<?> create(Type type, Set<? extends Annotation> annotations, Moshi moshi) {
+      @Override public @Nullable JsonAdapter<?> create(
+          Type type, Set<? extends Annotation> annotations, Moshi moshi) {
         Set<? extends Annotation> delegateAnnotations =
             Types.nextAnnotations(annotations, Enveloped.class);
         if (delegateAnnotations == null) {

examples/src/main/java/com/squareup/moshi/recipes/package-info.java

@@ -0,0 +1,3 @@
+/** Moshi code samples. */
+@javax.annotation.ParametersAreNonnullByDefault
+package com.squareup.moshi.recipes;