Hi All,
Please find comments inline.
Yes, this has been the case for sometime where internally append is used.
> Try the same with a loop.
+1 have tried this. Even though compiler is optimized to put StringBuilder
on multiple "+" concats not too *smart* to use the same StringBuilder
instance inside a loop.
Tried Test.java with a string concat inside a *loop*.
*Test.java*
class Test {
public static void main(String[] args) {
String content = "";
for (int i = 0; i < 10; i++) {
content = content + String.valueOf(i);
}
System.out.println(content);
}
}
*Constant pool:*
const #3 = class #24; // java/lang/StringBuilder
*Main Method:*
public static void main(java.lang.String[]);
Code:
0: ldc #2; //String
2: astore_1
3: iconst_0
4: istore_2
5: iload_2
6: bipush 10
8: if_icmpge 39
11: new #3; //class java/lang/StringBuilder <-------*creating new String
builder each cycle*
14: dup
15: invokespecial #4; //Method java/lang/StringBuilder."<init>":()V
18: aload_1
19: invokevirtual #5; //Method
java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
22: iload_2
23: invokestatic #6; //Method
java/lang/String.valueOf:(I)Ljava/lang/String;
26: invokevirtual #5; //Method
java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
29: invokevirtual #7; //Method
java/lang/StringBuilder.toString:()Ljava/lang/String;
32: astore_1
33: iinc 2, 1
36: goto 5 <--------------- *Jump for the loop*
39: getstatic #8; //Field java/lang/System.out:Ljava/io/PrintStream;
42: aload_1
43: invokevirtual #9; //Method
java/io/PrintStream.println:(Ljava/lang/String;)V
46: return
}
Thanks,
Rasika
On Wed, Dec 16, 2015 at 6:19 AM, Afkham Azeez <az...@wso2.com> wrote:
> Yes, this has been the case for sometime where internally append is used.
> Try the same with a loop.
>
> On Tue, Dec 15, 2015 at 11:43 PM, Manuranga Perera <m...@wso2.com> wrote:
>
>> I have compiled following class using javac 1.6.0_38
>>
>> class X{
>> public String m(String a, String b, String c){
>> return a + b + c;
>> }
>> }
>>
>>
>> and decoupled using javap
>>
>>
>> class X {
>> X();
>> Code:
>> 0: aload_0
>> 1: invokespecial #1 // Method
>> java/lang/Object."<init>":()V
>> 4: return
>>
>> public java.lang.String m(java.lang.String, java.lang.String,
>> java.lang.String);
>> Code:
>> 0: new #2 // class
>> java/lang/StringBuilder
>> 3: dup
>> 4: invokespecial #3 // Method
>> java/lang/StringBuilder."<init>":()V
>> 7: aload_1
>> 8: invokevirtual #4 // Method
>> java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
>> 11: aload_2
>> 12: invokevirtual #4 // Method
>> java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
>> 15: aload_3
>> 16: invokevirtual #4 // Method
>> java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
>> 19: invokevirtual #5 // Method
>> java/lang/StringBuilder.toString:()Ljava/lang/String;
>> 22: areturn
>> }
>>
>> As you can see, there are three appends but only one StringBuilder
>> objects. Therefor I purpose using plus instead of append in our code.
>>
>>
>>
>> --
>> With regards,
>> *Manu*ranga Perera.
>>
>> phone : 071 7 70 20 50
>> mail : m...@wso2.com
>>
>
>
>
> --
> *Afkham Azeez*
> Director of Architecture; WSO2, Inc.; http://wso2.com
> Member; Apache Software Foundation; http://www.apache.org/
> * <http://www.apache.org/>*
> *email: **az...@wso2.com* <az...@wso2.com>
> * cell: +94 77 3320919 <%2B94%2077%203320919>blog: *
> *http://blog.afkham.org* <http://blog.afkham.org>
> *twitter: **http://twitter.com/afkham_azeez*
> <http://twitter.com/afkham_azeez>
> *linked-in: **http://lk.linkedin.com/in/afkhamazeez
> <http://lk.linkedin.com/in/afkhamazeez>*
>
> *Lean . Enterprise . Middleware*
>
> _______________________________________________
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> Dev@wso2.org
> http://wso2.org/cgi-bin/mailman/listinfo/dev
>
>
--
With Regards,
*Rasika Perera*
Software Engineer
M: +94 71 680 9060 E: rasi...@wso2.com
LinkedIn: http://lk.linkedin.com/in/rasika90
WSO2 Inc. www.wso2.com
lean.enterprise.middleware
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