The Java API (Application Programming Interface) has thousands of identifiers. Each identifier is the name of something (a class, an object, a method, or something like that). These identifiers include
System, out, println, String, toString, JFrame, File, Scanner, next, nextInt, Exception, close, ArrayList, stream, JTextField, Math, Random, MenuItem, Month, parseInt, Query, Rectangle, Color, Oval, paint, Robot, SQLData, Stack, Queue, TimeZone, URL, and so many others.You can reuse any of these names for any purpose in your code. But if you do, you might have trouble using a name with its normal meaning from the Java API. For example, you can write
int System = 7;
java.lang.System.out.println(System);
But you can't write
int System = 7;
System.out.println(System);
