StringBuffer replacing String for memory Issues Help!!

[VigneshMohan]

Hi All

I wanted to replace the String Concatenation using " + " with a string buffer to eliminate performance hogs.

I have a string

String str = "Testing "+ firstStrVariabl e + "NextTest" + secondStringVar iable + "ThirdTest" ;

Is it worth replacing the String in this case with StringBuffer and StringBuffer.Ap pend

Any Suggestions pl post it
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Thanks
Vignesh.M

[JosAH]

@VigneshMohan
If at least one of the operands of the + operator is a String the compiler plays a few tricks: it uses a StringBuffer (or StringBuilder) to catenate the Strings. If you don't want to add Strings a million times you can safely use the + operator. Otherwise use the sb.append() method repeatedly.

kind regards,

Jos

[VigneshMohan]

@JosAH
Hi
JosAH

But appending a string using " + " will create a new string object right

Which all cases will create a new string object with the use of + ?

Will all the different arise only when we use threads?

In other cases are these all same. ?
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Thanks
Vignesh.M

[JosAH]

@VigneshMohan
If a, b and c are Strings and you want to 'add' them, the compiler will generate the following:

String a, b, c;
String result= new StringBuffer(new StringBuffer(a).append(b).toString()).append(c).toString();
 

Manually you could do this with just one StringBuffer:

String a, b, c;
String result= new StringBuffer(a).append(b).append(c).toString();
 

Note that this all has nothing to do with Threads.

kind regards,

Jos

[VigneshMohan]

@JosAH


Great ...

I need one more clarification

If I give like this

String aStringVariable = "welcome";
String test = "sample"+aStringVariable+"sample2";
 

What will the compiler do...?
If we give constants how the compiler interprets internally?

One more Doubt.

StringBuffer is Synchronous and StringBuilder is Unsynchronous
Could you explain this?

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Thanks

Vignesh.M

[JosAH]

@VigneshMohan
If the compiler sees a + operator with String operands it generates a StringBuffer given the left String operand; appends the right String operand and retrieves the (new) String by invoking the toString() method on that StringBuffer. If it sees another + operator it'll simply do the same (also see my previous reply).

If you use one Thread only for your StringBuffer operations you can better use a StringBuilder because the latter doesn't synchronize its methods (compare with Vector and ArrayList).

kind regards,

Jos