[GitHub] [pulsar] mattisonchao edited a comment on pull request #10986: Fixed # fixed string concatation in loop.

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mattisonchao edited a comment on pull request #10986:
URL: https://github.com/apache/pulsar/pull/10986#issuecomment-870936897


   > Did you see some measurable improvement?
   > 
   > I am saying this because recently JVM handle string concatenation better that using StringBuilder in same cases and forcing a concatenation strategy sometimes it is not the best option.
   > 
   > That said I am not against this change, but I just want to know if this is the result of some static code analysis or it is fixing a real problem. You know the motto 'don't fix things that are not broken
   
   Yes, I test it in a small example. when you use a string connection inline, the JVM will translate it to `StringBuilder` and invoke the `append` method to handle it.
   the bytecode is as follows:
   ```java
     L0
       LINENUMBER 6 L0
       LDC "abc"
       ASTORE 1
      L1
       LINENUMBER 7 L1
       NEW java/lang/StringBuilder
       DUP
       INVOKESPECIAL java/lang/StringBuilder.<init> ()V
       ALOAD 1
       INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;
       LDC "d"
       INVOKEVIRTUAL java/lang/StringBuilder.append (Ljava/lang/String;)Ljava/lang/StringBuilder;
       INVOKEVIRTUAL java/lang/StringBuilder.toString ()Ljava/lang/String;
       ASTORE 1
      L2
       LINENUMBER 10 L2
       GETSTATIC java/lang/System.out : Ljava/io/PrintStream;
       ALOAD 1
       INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V
      L3
       LINENUMBER 11 L3
       RETURN
      L4
       LOCALVARIABLE args [Ljava/lang/String; L0 L4 0
       LOCALVARIABLE a Ljava/lang/String; L1 L4 1
       MAXSTACK = 2
       MAXLOCALS = 2
   ```


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