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
-

Thanks
Vignesh.M

[JosAH]

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
-

Thanks
Vignesh.M

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]

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

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. ?
-
Thanks
Vignesh.M

[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. ?
-
Thanks
Vignesh.M

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]

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

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?

-
Thanks

Vignesh.M

[JosAH]

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?

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