8260273: DataOutputStream writeChars optimization

Reviewed-by: rriggs, bpb, alanb

Author: Hamlin Li

src/java.base/share/classes/java/io/DataOutputStream.java

@@ -300,8 +300,9 @@ public final void writeChars(String s) throws IOException {
         int len = s.length();
         for (int i = 0 ; i < len ; i++) {
             int v = s.charAt(i);
-            out.write((v >>> 8) & 0xFF);
-            out.write((v >>> 0) & 0xFF);
+            writeBuffer[0] = (byte)(v >>> 8);
+            writeBuffer[1] = (byte)(v >>> 0);
+            out.write(writeBuffer, 0, 2);
         }
         incCount(len * 2);
     }

test/micro/org/openjdk/bench/java/io/DataOutputStreamTest.java

@@ -37,7 +37,7 @@
 public class DataOutputStreamTest {
 
     public enum BasicType {CHAR, SHORT, INT, STRING}
-    @Param({"CHAR", "SHORT", "INT", /* "STRING"*/}) BasicType basicType;
+    @Param({"CHAR", "SHORT", "INT", "STRING"}) BasicType basicType;
 
     @Param({"4096"}) int size;
     final ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(size);