Using the Scanner Class

To make Java programs interactive, you will want to ask and receive input from the user.  Java has a class that accepts user input called Scanner. Before you can use the Scanner class in a program, you must import it. To do that, you code an import statement at the beginning of the program, before the class declaration: import java.util.Scanner; Note that java and util aren’t capitalized, but Scanner is.

Before you can use the Scanner class to read input from the console, you must declare a Scanner variable and create an instance of the Scanner class. You might want to create the Scanner variable as a class variable and create the Scanner object in the class variable initializer: Scanner scan = new Scanner(System.in);   To read an input value from the user, you can use one of the methods of the Scanner class.

Scanner Class Methods

Scanner Class Methods That Get Input Values Method                                                                Explanation boolean nextBoolean()                           Reads a boolean value from the user. double nextDouble()                                Reads a double value from the user. int nextInt()                                                   Reads an int value from the user. String nextLine()                                       Reads a String value from the user. char nextChar()                                          Reads a char value from the user.

Notice in the first column of the table that each method listing begins with the type of the value that’s returned by the method. The nextInt method, for example, returns an int value. Also, notice that each of the methods ends with an empty set of parentheses. That means that these methods don’t require parameters. If a method does require parameters, the parameters are listed within these parentheses.

Because these methods read a value from the user and return the value, you most often use them in statements that assign the value to a variable. To store the input from the user, you would use a System.out.print to prompt the user.  For example: System.out.print(“How old are you?);   Then you would capture the input into a variable: int age = scan.nextInt();   Note the age variable could have been declared separately at the top of the program, or in combination with the initialization as shown in this example.