Java How to Program (early objects), 9/e

16.4 Class StringBuilder

We now discuss the features of class StringBuilder for creating and manipulating dynamic string information—that is, modifiable strings. Every StringBuilder is capable of storing a number of characters specified by its capacity. If a StringBuilder’s capacity is exceeded, the capacity expands to accommodate the additional characters.

Performance Tip 16.2

Java can perform certain optimizations involving String objects (such as referring to one String object from multiple variables) because it knows these objects will not change. Strings (not StringBuilders) should be used if the data will not change.

Performance ...