Remove dynamic calls to FindClass.

Initially, I was just fixing a threading bug in NativeDecimalFormat.cpp where
we were bypassing GCC's built-in static initializer thread safety. This led me
to the question of how expensive FindClass is, which led me to creating a new
canonical cache of jclasses.

Here's the motivating benchmark, showing the cost of calling an empty regular
(non-native) method, an empty native method, a native method that calls
FindClass, a native method that calls FindClass and GetFieldID, and a native
method that calls FindClass and GetMethodID:

             benchmark    ns logarithmic runtime
         NoArgsRegular    74 ||||||||||||||
          NoArgsNative   428 XX|||||||||||||||||||
             FindClass  3064 XXXXXXXXXXXXXXXX|||||||||||
     FindClassGetField  3654 XXXXXXXXXXXXXXXXXXX|||||||||
    FindClassGetMethod  5634 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Change-Id: I41ab2b347895f043a7e21d8fa19e4541e198c3fc

1 files changed, 6 insertions, 5 deletions

diff --git a/luni/src/main/native/BidiWrapper.cpp b/luni/src/main/native/BidiWrapper.cpp
index 59dcfaa..f703586 100644
--- a/luni/src/main/native/BidiWrapper.cpp
+++ b/luni/src/main/native/BidiWrapper.cpp
@@ -16,11 +16,13 @@
  */
 #define LOG_TAG "BidiWrapper"
 
-#include <JNIHelp.h>
 #include "ErrorCode.h"
+#include "JNIHelp.h"
+#include "JniConstants.h"
 #include "ScopedPrimitiveArray.h"
 #include "UniquePtr.h"
 #include "unicode/ubidi.h"
+
 #include <stdlib.h>
 #include <string.h>
 
@@ -135,15 +137,14 @@ static jobjectArray BidiWrapper_ubidi_getRuns(JNIEnv* env, jclass, jlong ptr) {
     if (icu4jni_error(env, err)) {
         return NULL;
     }
-    jclass bidiRunClass = env->FindClass("org/apache/harmony/text/BidiRun");
-    jmethodID bidiRunConstructor = env->GetMethodID(bidiRunClass, "<init>", "(III)V");
-    jobjectArray runs = env->NewObjectArray(runCount, bidiRunClass, NULL);
+    jmethodID bidiRunConstructor = env->GetMethodID(JniConstants::bidiRunClass, "<init>", "(III)V");
+    jobjectArray runs = env->NewObjectArray(runCount, JniConstants::bidiRunClass, NULL);
     UBiDiLevel level = 0;
     int start = 0;
     int limit = 0;
     for (int i = 0; i < runCount; ++i) {
         ubidi_getLogicalRun(ubidi, start, &limit, &level);
-        jobject run = env->NewObject(bidiRunClass, bidiRunConstructor, start, limit, level);
+        jobject run = env->NewObject(JniConstants::bidiRunClass, bidiRunConstructor, start, limit, level);
         env->SetObjectArrayElement(runs, i, run);
         start = limit;
     }