util-registry: Java-friendly API for Registry

Problem
There is no Java-friendly API for `Registry.put`. The only way to
put a value into a registry from Java is to use the following pattern.

Solution
Use `@varargs` annotation to provide a Java-friendly version of `put`.

RB_ID=749845

util-registry/BUILD

@@ -8,6 +8,7 @@ target(name='util-registry',
 
 target(name='tests',
   dependencies=[
-    'util/util-registry/src/test/scala'
+    'util/util-registry/src/test/scala',
+    'util/util-registry/src/test/java'
   ]
 )

util-registry/src/main/scala/com/twitter/util/registry/Registry.scala

@@ -1,7 +1,7 @@
 package com.twitter.util.registry
 
-import java.util.NoSuchElementException
 import com.twitter.util.Local
+import scala.annotation.varargs
 
 /**
  * This is an expert-level API; it is not meant for end-users.
@@ -36,10 +36,24 @@ trait Registry extends Iterable[Entry] {
   def iterator: Iterator[Entry]
 
   /**
-   * Registers a value in the registry, and returns the old value (if any).
+   * Registers a  value in the registry, and returns the old value (if any).
+   *
+   * See `Registry.put(String*)` for the Java usage.
    */
   def put(key: Seq[String], value: String): Option[String]
 
+  /**
+   * Registers a value (a non-empty sequence of strings) in the registry, and returns the old
+   * value (if any).
+   *
+   * Note: This is a Java-friendly version of `Registry.put(Seq[String, String])`.
+   */
+  @varargs
+  def put(value: String*): Option[String] = {
+    require(value.nonEmpty)
+    put(value.init, value.last)
+  }
+
   /**
    * Removes a key from the registry, if it was registered, and returns the old value (if any).
    */

util-registry/src/test/java/BUILD

@@ -0,0 +1,8 @@
+junit_tests(name='java',
+  dependencies=[
+    '3rdparty/jvm/org/scala-lang:scala-library',
+    '3rdparty/jvm/junit',
+    'util/util-registry/src/main/scala',
+  ],
+  sources=rglobs('*.java')
+)

util-registry/src/test/java/com/twitter/util/registry/RegistryCompilationTest.java

@@ -0,0 +1,16 @@
+package com.twitter.util.registry;
+
+import com.twitter.util.registry.GlobalRegistry;
+import com.twitter.util.registry.Registry;
+import org.junit.Test;
+
+public class RegistryCompilationTest {
+
+  @Test
+  public void testPut() {
+    Registry registry = GlobalRegistry.get();
+    registry.put("foo", "bar", "baz");
+    registry.put("foo", "qux");
+    registry.put("baz");
+  }
+}

util-registry/src/test/scala/com/twitter/util/registry/RegistryTest.scala

@@ -26,7 +26,7 @@ abstract class RegistryTest extends FunSuite {
     val registry = mkRegistry()
     registry.put(Seq("foo"), "bar")
     registry.put(Seq("foo"), "baz")
-    assert((registry.toSet) == Set(Entry(Seq("foo"), "baz")))
+    assert(registry.toSet == Set(Entry(Seq("foo"), "baz")))
   }
 
   test(s"$name can return the old element when replacing") {
@@ -40,7 +40,7 @@ abstract class RegistryTest extends FunSuite {
     val registry = mkRegistry()
     registry.put(Seq("foo"), "bar")
     assert(registry.remove(Seq("foo")) == Some("bar"))
-    assert((registry.toSet) == Set.empty)
+    assert(registry.toSet == Set.empty)
   }
 
   test(s"$name can remove nothing") {
@@ -94,4 +94,11 @@ abstract class RegistryTest extends FunSuite {
     registry.put(Seq("foo", "baz"), "qux")
     assert(registry.toSet == Set(Entry(Seq("foo"), "bar"), Entry(Seq("foo", "baz"), "qux")))
   }
+
+  test(s"$name can support varargs API") {
+    val registry = mkRegistry()
+    registry.put("foo", "bar", "baz")
+    registry.put("qux")
+    assert(registry.toSet == Set(Entry(Seq("foo", "bar"), "baz"), Entry(Seq(), "qux")))
+  }
 }