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A Scanner object can parse user input entered on the console or from a file. A Scanner breaks its input into separate tokens (which are typically separated by white space), and then returns them one at a time. The scanner provides methods to convert the tokens into values of different types.
Chapter 2 Basics of Scanning and Conventional Programming in Java In this chapter, we will introduce you to an initial set of Java features, the equivalent of which you should have seen in your CS-1 class; the separation of problem, representation, algorithm and program
Using the Scanner Class •Provides methods for reading byte, short, int, long, float, double, and String data types from the user. •Scanner is in the java.util package •Scanner parses (separates) input into sequences of characters called tokens. •By default, tokens are separated by standard white space characters (tab, space, newline, etc.)
interactive program: Reads input from the console. While the program runs, it asks the user to type input. The input typed by the user is stored in variables in the code. Can be tricky; users are unpredictable and misbehave. But interactive programs have more interesting behavior. Each method waits until the user presses Enter.
In Java, two interfaces exist to give structure to bits of input data: InputStream to read input byte by byte, and Scanner to read input using more complex data types. Java’s InputStream interface can be used in a program to read input byte per input byte.
For example, when retrieving user input from the keyboard, we do not have to interact with the hardware and deal with all of the event handling necessary to retrieve user input from the keyboard. Instead, we just have to create a Scanner object that does all of that for us. Scanner scan = new Scanner(System.in);
The primary function of a scanner is to read in characters from a source file and group them into tokens. A scanner is sometimes called a lexical analyzer or lexer. The names scanner, lexical analyzer and lexer
