Add toJavaUtil instance method, which is handier and also doesn't have to be

marked @Nullable.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=140905873

3 files changed, 38 insertions, 6 deletions

diff --git a/guava-gwt/test/com/google/common/base/OptionalTest_gwt.java b/guava-gwt/test/com/google/common/base/OptionalTest_gwt.java
index 1bebbb9cc..e8bdb1a13 100644
--- a/guava-gwt/test/com/google/common/base/OptionalTest_gwt.java
+++ b/guava-gwt/test/com/google/common/base/OptionalTest_gwt.java
@@ -193,9 +193,14 @@ public void testSampleCodeFine2() throws Exception {
   testCase.testSampleCodeFine2();
 }
 
-public void testToJavaUtil() throws Exception {
+public void testToJavaUtil_instance() throws Exception {
   com.google.common.base.OptionalTest testCase = new com.google.common.base.OptionalTest();
-  testCase.testToJavaUtil();
+  testCase.testToJavaUtil_instance();
+}
+
+public void testToJavaUtil_static() throws Exception {
+  com.google.common.base.OptionalTest testCase = new com.google.common.base.OptionalTest();
+  testCase.testToJavaUtil_static();
 }
 
 public void testToString_absent() throws Exception {
diff --git a/guava-tests/test/com/google/common/base/OptionalTest.java b/guava-tests/test/com/google/common/base/OptionalTest.java
index 007841fbb..8f7de2110 100644
--- a/guava-tests/test/com/google/common/base/OptionalTest.java
+++ b/guava-tests/test/com/google/common/base/OptionalTest.java
@@ -36,12 +36,17 @@ import junit.framework.TestCase;
  */
 @GwtCompatible(emulated = true)
 public final class OptionalTest extends TestCase {
-  public void testToJavaUtil() {
+  public void testToJavaUtil_static() {
     assertNull(Optional.toJavaUtil(null));
     assertEquals(java.util.Optional.empty(), Optional.toJavaUtil(Optional.absent()));
     assertEquals(java.util.Optional.of("abc"), Optional.toJavaUtil(Optional.of("abc")));
   }
 
+  public void testToJavaUtil_instance() {
+    assertEquals(java.util.Optional.empty(), Optional.absent().toJavaUtil());
+    assertEquals(java.util.Optional.of("abc"), Optional.of("abc").toJavaUtil());
+  }
+
   public void testFromJavaUtil() {
     assertNull(Optional.fromJavaUtil(null));
     assertEquals(Optional.absent(), Optional.fromJavaUtil(java.util.Optional.empty()));
diff --git a/guava/src/com/google/common/base/Optional.java b/guava/src/com/google/common/base/Optional.java
index 6b18e959d..96d82baa9 100644
--- a/guava/src/com/google/common/base/Optional.java
+++ b/guava/src/com/google/common/base/Optional.java
@@ -121,6 +121,8 @@ public abstract class Optional<T> implements Serializable {
   /**
    * Returns the equivalent {@code com.google.common.base.Optional} value to the given {@code
    * java.util.Optional}, or {@code null} if the argument is null.
+   *
+   * @since 21.0
    */
   @Nullable
   public static <T> Optional<T> fromJavaUtil(@Nullable java.util.Optional<T> javaUtilOptional) {
@@ -130,12 +132,19 @@ public abstract class Optional<T> implements Serializable {
   /**
    * Returns the equivalent {@code java.util.Optional} value to the given {@code
    * com.google.common.base.Optional}, or {@code null} if the argument is null.
+   *
+   * <p>If {@code googleOptional} is known to be non-null, use {@code googleOptional.toJavaUtil()}
+   * instead.
+   *
+   * <p>Unfortunately, the method reference {@code Optional::toJavaUtil} will not work, because it
+   * could refer to either the static or instance version of this method. Write out the lambda
+   * expression {@code o -> Optional.toJavaUtil(o)} instead.
+   *
+   * @since 21.0
    */
   @Nullable
   public static <T> java.util.Optional<T> toJavaUtil(@Nullable Optional<T> googleOptional) {
-    return (googleOptional == null)
-        ? null
-        : java.util.Optional.ofNullable(googleOptional.orNull());
+    return googleOptional == null ? null : googleOptional.toJavaUtil();
   }
 
   Optional() {}
@@ -263,6 +272,19 @@ public abstract class Optional<T> implements Serializable {
   public abstract <V> Optional<V> transform(Function<? super T, V> function);
 
   /**
+   * Returns the equivalent {@code java.util.Optional} value to this optional.
+   *
+   * <p>Unfortunately, the method reference {@code Optional::toJavaUtil} will not work, because it
+   * could refer to either the static or instance version of this method. Write out the lambda
+   * expression {@code o -> o.toJavaUtil()} instead.
+   *
+   * @since 21.0
+   */
+  public java.util.Optional<T> toJavaUtil() {
+    return java.util.Optional.ofNullable(orNull());
+  }
+
+  /**
    * Returns {@code true} if {@code object} is an {@code Optional} instance, and either the
    * contained references are {@linkplain Object#equals equal} to each other or both are absent.
    * Note that {@code Optional} instances of differing parameterized types can be equal.