Final answer:
In Java, PrintStream belongs to the java.io package, and String is part of the java.lang package. Rectangle and Circle are usually custom classes.
Step-by-step explanation:
The given question involves identifying which class belongs to a specific package. In the context of Java programming, classes such as Rectangle and Circle are typically not part of the standard Java API, but rather they are custom classes created by users or part of graphics libraries. The class PrintStream is a part of the java.io package, which provides classes for system input and output through data streams, serialization and the file system. String is part of the java.lang package, which is automatically imported into all Java programs.