JDK 10 RFR JDK-8174267: Stream.findFirst unnecessarily always allocates an Op

[Ron Pressler]

Hi.
Please review the following patch, which creates static final instances 
of FindOp.

Bug: https://bugs.openjdk.java.net/browse/JDK-8174267

I believe an additional test is not required as this is an 
implementation detail.

-------
diff -r 83d37efcd2a5 
src/java.base/share/classes/java/util/stream/FindOps.java
--- a/src/java.base/share/classes/java/util/stream/FindOps.java Thu Apr 
13 20:35:17 2017 +0000
+++ b/src/java.base/share/classes/java/util/stream/FindOps.java Fri Apr 
28 19:28:36 2017 +0000
@@ -54,9 +54,10 @@
       *        first element in the encounter order
       * @return a {@code TerminalOp} implementing the find operation
       */
+    @SuppressWarnings("unchecked")
      public static <T> TerminalOp<T, Optional<T>> makeRef(boolean 
mustFindFirst) {
-        return new FindOp<>(mustFindFirst, StreamShape.REFERENCE, 
Optional.empty(),
-                            Optional::isPresent, FindSink.OfRef::new);
+        return (TerminalOp<T, Optional<T>>)
+                (mustFindFirst ? FindSink.OfRef.OP_FIND_FIRST : 
FindSink.OfRef.OP_FIND_ANY);
      }

      /**
@@ -67,8 +68,7 @@
       * @return a {@code TerminalOp} implementing the find operation
       */
      public static TerminalOp<Integer, OptionalInt> makeInt(boolean 
mustFindFirst) {
-        return new FindOp<>(mustFindFirst, StreamShape.INT_VALUE, 
OptionalInt.empty(),
-                            OptionalInt::isPresent, FindSink.OfInt::new);
+        return mustFindFirst ? FindSink.OfInt.OP_FIND_FIRST : 
FindSink.OfInt.OP_FIND_ANY;
      }

      /**
@@ -79,8 +79,7 @@
       * @return a {@code TerminalOp} implementing the find operation
       */
      public static TerminalOp<Long, OptionalLong> makeLong(boolean 
mustFindFirst) {
-        return new FindOp<>(mustFindFirst, StreamShape.LONG_VALUE, 
OptionalLong.empty(),
-                            OptionalLong::isPresent, FindSink.OfLong::new);
+        return mustFindFirst ? FindSink.OfLong.OP_FIND_FIRST : 
FindSink.OfLong.OP_FIND_ANY;
      }

      /**
@@ -91,8 +90,7 @@
       * @return a {@code TerminalOp} implementing the find operation
       */
      public static TerminalOp<Double, OptionalDouble> 
makeDouble(boolean mustFindFirst) {
-        return new FindOp<>(mustFindFirst, StreamShape.DOUBLE_VALUE, 
OptionalDouble.empty(),
-                            OptionalDouble::isPresent, 
FindSink.OfDouble::new);
+        return mustFindFirst ? FindSink.OfDouble.OP_FIND_FIRST : 
FindSink.OfDouble.OP_FIND_ANY;
      }

      /**
@@ -195,6 +193,14 @@
              public Optional<T> get() {
                  return hasValue ? Optional.of(value) : null;
              }
+
+            static final TerminalOp<?, ?> OP_FIND_FIRST = new 
FindOp<>(true,
+                    StreamShape.REFERENCE, Optional.empty(),
+                    Optional::isPresent, FindSink.OfRef::new);
+
+            static final TerminalOp<?, ?> OP_FIND_ANY = new FindOp<>(false,
+                    StreamShape.REFERENCE, Optional.empty(),
+                    Optional::isPresent, FindSink.OfRef::new);
          }

          /** Specialization of {@code FindSink} for int streams */
@@ -210,6 +216,13 @@
              public OptionalInt get() {
                  return hasValue ? OptionalInt.of(value) : null;
              }
+
+            static final TerminalOp<Integer, OptionalInt> OP_FIND_FIRST 
= new FindOp<>(true,
+                    StreamShape.INT_VALUE, OptionalInt.empty(),
+                    OptionalInt::isPresent, FindSink.OfInt::new);
+            static final TerminalOp<Integer, OptionalInt> OP_FIND_ANY = 
new FindOp<>(false,
+                    StreamShape.INT_VALUE, OptionalInt.empty(),
+                    OptionalInt::isPresent, FindSink.OfInt::new);
          }

          /** Specialization of {@code FindSink} for long streams */
@@ -225,6 +238,13 @@
              public OptionalLong get() {
                  return hasValue ? OptionalLong.of(value) : null;
              }
+
+            static final TerminalOp<Long, OptionalLong> OP_FIND_FIRST = 
new FindOp<>(true,
+                    StreamShape.LONG_VALUE, OptionalLong.empty(),
+                    OptionalLong::isPresent, FindSink.OfLong::new);
+            static final TerminalOp<Long, OptionalLong> OP_FIND_ANY = 
new FindOp<>(false,
+                    StreamShape.LONG_VALUE, OptionalLong.empty(),
+                    OptionalLong::isPresent, FindSink.OfLong::new);
          }

          /** Specialization of {@code FindSink} for double streams */
@@ -240,6 +260,13 @@
              public OptionalDouble get() {
                  return hasValue ? OptionalDouble.of(value) : null;
              }
+
+            static final TerminalOp<Double, OptionalDouble> 
OP_FIND_FIRST = new FindOp<>(true,
+                    StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
+                    OptionalDouble::isPresent, FindSink.OfDouble::new);
+            static final TerminalOp<Double, OptionalDouble> OP_FIND_ANY 
= new FindOp<>(false,
+                    StreamShape.DOUBLE_VALUE, OptionalDouble.empty(),
+                    OptionalDouble::isPresent, FindSink.OfDouble::new);
          }
      }

-------

Ron