[GitHub] [incubator-zipkin] adriancole commented on a change in pull request #2591: Let Java copy arrays which it can sometimes do faster than manual loops.

[GitBox <gi...@apache.org>]

adriancole commented on a change in pull request #2591: Let Java copy arrays which it can sometimes do faster than manual loops.
URL: https://github.com/apache/incubator-zipkin/pull/2591#discussion_r283657086
 
 

 ##########
 File path: zipkin/src/main/java/zipkin2/Span.java
 ##########
 @@ -659,11 +659,21 @@ public static String normalizeTraceId(String traceId) {
     }
   }
 
+  static final String THIRTY_TWO_ZEROS;
+  static {
+    char[] zeros = new char[32];
+    Arrays.fill(zeros, '0');
+    THIRTY_TWO_ZEROS = new String(zeros);
+  }
+
   static String padLeft(String id, int desiredLength) {
+    int length = id.length();
+    int numZeros = desiredLength - length;
+
     char[] data = Platform.shortStringBuffer();
-    int i = 0, length = id.length(), offset = desiredLength - length;
-    for (; i < offset; i++) data[i] = '0';
-    for (int j = 0; j < length; j++) data[i++] = id.charAt(j);
+    THIRTY_TWO_ZEROS.getChars(0, numZeros, data, 0);
+    id.getChars(0, length, data, numZeros);
 
 Review comment:
   heh never knew about this method before. nice one!

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