mattisonchao commented on pull request #10986:
URL: https://github.com/apache/pulsar/pull/10986#issuecomment-870939519
> 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
But if you try to connect String in a loop, they will create a lot of
StringBuilder Object.
the bytecode is as follows:
```java
L0
LINENUMBER 6 L0
LDC "abc"
ASTORE 1
L1
LINENUMBER 7 L1
ICONST_0
ISTORE 2
L2
FRAME APPEND [java/lang/String I]
ILOAD 2
BIPUSH 10
IF_ICMPGE L3
L4
LINENUMBER 8 L4
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
L5
LINENUMBER 7 L5
IINC 2 1
GOTO L2
L3
LINENUMBER 10 L3
FRAME CHOP 1
GETSTATIC java/lang/System.out : Ljava/io/PrintStream;
ALOAD 1
INVOKEVIRTUAL java/io/PrintStream.println (Ljava/lang/String;)V
L6
LINENUMBER 11 L6
RETURN
L7
LOCALVARIABLE i I L2 L3 2
LOCALVARIABLE args [Ljava/lang/String; L0 L7 0
LOCALVARIABLE a Ljava/lang/String; L1 L7 1
MAXSTACK = 2
MAXLOCALS = 3
```
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