Add default implementations of deprecated methods of BuilableItem and Item.

core/src/main/java/hudson/Functions.java

@@ -1143,16 +1143,17 @@ public static List<TopLevelItem> getAllTopLevelItems(ItemGroup root) {
      * Gets the relative name or display name to the given item from the specified group.
      *
      * @since 1.515
-     * @param p the Item we want the relative display name
+     * @param p the Item we want the relative display name.
+     *          If {@code null}, a {@code null} will be returned by the method
      * @param g the ItemGroup used as point of reference for the item.
      *          If the group is not specified, item's path will be used.
      * @param useDisplayName if true, returns a display name, otherwise returns a name
      * @return
      *      String like "foo » bar".
-     *      {@code null} if item is null or if one of its parents is not an {@link ItemGroup}.
+     *      {@code null} if item is null or if one of its parents is not an {@link Item}.
      */
     @Nullable
-    public static String getRelativeNameFrom(Item p, ItemGroup g, boolean useDisplayName) {
+    public static String getRelativeNameFrom(@CheckForNull Item p, @CheckForNull ItemGroup g, boolean useDisplayName) {
         if (p == null) return null;
         if (g == null) return useDisplayName ? p.getFullDisplayName() : p.getFullName();
         String separationString = useDisplayName ? " » " : "/";
@@ -1196,13 +1197,14 @@ public static String getRelativeNameFrom(Item p, ItemGroup g, boolean useDisplay
      *
      * @since 1.515
      * @param p the Item we want the relative display name
+     *          If {@code null}, the method will immediately return {@code null}.
      * @param g the ItemGroup used as point of reference for the item
      * @return
      *      String like "foo/bar".
-     *      {@code null} if the item is {@code null} or if one of its parents is not an {@link ItemGroup}.
+     *      {@code null} if the item is {@code null} or if one of its parents is not an {@link Item}.
      */
     @Nullable
-    public static String getRelativeNameFrom(Item p, ItemGroup g) {
+    public static String getRelativeNameFrom(@CheckForNull Item p, @CheckForNull ItemGroup g) {
         return getRelativeNameFrom(p, g, false);
     }    
 
@@ -1211,14 +1213,15 @@ public static String getRelativeNameFrom(Item p, ItemGroup g) {
      * Gets the relative display name to the given item from the specified group.
      *
      * @since 1.512
-     * @param p the Item we want the relative display name
+     * @param p the Item we want the relative display name.
+     *          If {@code null}, the method will immediately return {@code null}.
      * @param g the ItemGroup used as point of reference for the item
      * @return
      *      String like "Foo » Bar".
-     *      {@code null} if the item is {@code null} or if one of its parents is not an {@link ItemGroup}.
+     *      {@code null} if the item is {@code null} or if one of its parents is not an {@link Item}.
      */
     @Nullable
-    public static String getRelativeDisplayNameFrom(Item p, ItemGroup g) {
+    public static String getRelativeDisplayNameFrom(@CheckForNull Item p, @CheckForNull ItemGroup g) {
         return getRelativeNameFrom(p, g, true);
     }
 

core/src/main/java/hudson/model/Item.java

@@ -30,6 +30,7 @@
 import jenkins.util.SystemProperties;
 import hudson.security.PermissionScope;
 import jenkins.util.io.OnMaster;
+import jline.internal.Nullable;
 import org.kohsuke.stapler.StaplerRequest;
 
 import java.io.IOException;
@@ -41,6 +42,9 @@
 import hudson.security.AccessControlled;
 import hudson.util.Secret;
 
+import javax.annotation.CheckForNull;
+import javax.annotation.Nonnull;
+
 /**
  * Basic configuration unit in Hudson.
  *
@@ -134,24 +138,28 @@ public interface Item extends PersistenceRoot, SearchableModelObject, AccessCont
      * Gets the relative name to this item from the specified group.
      *
      * @param g
-     *      The ItemGroup instance used as context to evaluate the relative name of this AbstractItem
+     *      The {@link ItemGroup} instance used as context to evaluate the relative name of this item
      * @return
-     *      The name of the current item, relative to p. Nested ItemGroups are separated by {@code /} character.
+     *      The name of the current item, relative to p. Nested {@link ItemGroup}s are separated by {@code /} character.
      * @since 1.419
      * @return
      *      String like "../foo/bar".
-     *      {@code null} if item parents is not an {@link ItemGroup}.
+     *      {@code null} if one of item parents is not an {@link Item}.
      */
-    default String getRelativeNameFrom(ItemGroup g) {
+    @Nullable
+    default String getRelativeNameFrom(@CheckForNull ItemGroup g) {
         return Functions.getRelativeNameFrom(this, g);
     }
 
     /**
      * Short for {@code getRelativeNameFrom(item.getParent())}
      *
+     * @return String like "../foo/bar".
+     *      {@code null} if one of item parents is not an {@link Item}.
      * @since 1.419
      */
-    default String getRelativeNameFrom(Item item)  {
+    @Nullable
+    default String getRelativeNameFrom(@Nonnull Item item)  {
         return getRelativeNameFrom(item.getParent());
 
     }