Final answer:
The DecimalFormat class is located in the java.text package of the Java standard library, which provides classes for text, date, number, and message handling.
Step-by-step explanation:
The DecimalFormat class is found inside the java.text package. This class is part of the Java programming language's standard library and is used to format decimal numbers into a string with a set number of decimal places, currency symbols, grouping separators, and more. The java.text package includes classes and interfaces for handling text, dates, numbers, and messages in a way that is independent of natural languages. This ensures that the same code can run regardless of the region or locale settings of the system it's running on.