Can we replace StringBuilder where we used StringBuffer in JDK1.5

[sumanta panda]

Dear All,

In our project we want to migrate from JDK1.4 TO JDK1.5.

We are using StringBuffer in our project.When we migrate JDK1.5 can we replace StringBuilder where we have used StringBuffer(For all the senario) for the performance?

Please suggest.

Thanks
Sumanta

[Rob Spoor]

StringBuffer has been retrofitted to extend class java.lang.AbstractStringBuilder (which is not public). Almost all methods actually just call the matching overridden method (e.g. append calls super.append). StringBuilder also extends AbstractStringBuilder, so it inherits those methods as well.

Now there may be a single method that isn't available in StringBuilder (but I doubt there is), so from the compiler's point of view you can safely replace StringBuffer with StringBuilder. Of course StringBuilder is not synchronized, so if you require that synchronization your code may fail at runtime.

[Henry Wong]

With Java 1.4, the Java compiler will use StringBuffer for all string concats (that use the "+" operator). With Java 5, the java compiler uses StringBuilder. So, a lot of your operations will switch from StringBuffer to StringBuilder automatically (upon recompile).

However, if you use StringBuffer explicitely, the java compiler will not automatically change it for you. The reason is, it doesn't know to what extend you are using it -- if you pass it elsewhere, then use it in a multithreaded format, switching to StringBuilder may break your app. Regardless, I wouldn't worry about it too much. Uncontended lock grabs have been greatly improved since Java 5, so using StringBuffer, single threaded, is probably not noticeable compared to using StringBuilder.

Henry