[GitHub] [incubator-seatunnel] ruanwenjun commented on a diff in pull request #1882: [Refactor][connector-doris] it's recommanded to use zero-length array parameter for list.toArray method for better performance

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ruanwenjun commented on code in PR #1882:
URL: https://github.com/apache/incubator-seatunnel/pull/1882#discussion_r873120843


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seatunnel-connectors/seatunnel-connectors-flink/seatunnel-connector-flink-doris/src/main/java/org/apache/seatunnel/flink/doris/sink/DorisOutputFormat.java:
##########
@@ -207,7 +207,7 @@ public synchronized void flush() throws IOException {
                 result = OBJECT_MAPPER.writeValueAsString(batch);
             }
         } else {
-            result = String.join(this.lineDelimiter, batch.toArray(new CharSequence[batch.size()]));
+            result = String.join(this.lineDelimiter, batch.toArray(new CharSequence[0]));

Review Comment:
   I don't think this change will get a better performance. 
   1. If we use `new CharSequence[0]`, it will create a extra Object array with length `batch.size()` and copy the element from batch to new array. 
   2. If we use `new CharSequence[batch.size()]`, it will just copy the element from batch to the given array.
   ```java
   public <T> T[] toArray(T[] a) {
       if (a.length < size)
           // Make a new array of a's runtime type, but my contents:
           return (T[]) Arrays.copyOf(elementData, size, a.getClass());
       System.arraycopy(elementData, 0, a, 0, size);
       if (a.length > size)
           a[size] = null;
       return a;
   }
   ```
   I don't think this change is necessary unless you can provide a benchmark test result. 



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