When does StringBuffer adds strings to the String Pool?

Question

When I define a StringBuffer variable with new, this string is not added to the String pool, right?

Now, when I define another StringBuffer but not with new, I define it as StrPrev.append("XXX") suddenly it is.(or so says my college teacher). Why is that? What makes this string to suddenly become a string-pool string?

Answer 1

When I define a StringBuffer variable with new, this string is not added to the String pool, right?

Creating a StringBuffer does not create a String at all.

Now, when I define another StringBuffer but not with new, I define it as StrPrev.append("XXX") suddenly it is.

This is totally confused:

• When you call strBuff.append("XXX") you are NOT defining a new StringBuffer. You are updating the existing StringBuffer that strBuff refers to. Specifically, you are adding extra characters to the end of the buffer.

• You only get a new String from the StringBuffer when you call strBuff.toString().

• You only add a String to the string pool when you call intern() on the String. And that only adds the string to the pool if there is not already an equal string in the pool.

• The String object that represents the literal "XXX" is a member of the string pool. But that happens (i.e. the String is added to the pool) when the class is loaded, not when you execute the append call.

(If you teacher told you that StringBuffer puts strings into the Java string pool, he / she is wrong. But, given your rather garbled description, I suspect that you actually misheard or misunderstood what your teacher really said.)