Today’s topics: I/O (Input/Output)

Scribbler Inputs & Outputs  What are the Scribbler’s inputs and outputs?  reset button  motors/wheel  light sensor  speaker  LEDs  stall sensor  obstacle sensor = emitter + detector  line sensor

Scribbler Inputs

Scribbler Outputs

Is the serial port an input, an output, or both?

What outputs does our computer have?

1. write / print / draw to monitor / screen / display 2. speaker for sound 3. write information to disks (hard, CD, and DVD) 4. write information to network interface card (NIC)

What outputs does our computer have? How do we perform output to the display in Java?

What outputs does our computer have? How do we perform output to the display in Java?  System.out.print  System.out.println

What inputs does our computer have?

1. mouse (movement and buttons) 2. keyboard 3. read information from disks (hard, CD, and DVD) 4. read information from network interface card (NIC)

What inputs does our computer have? We will now focus on reading information from the keyboard.

Input/Output  Input from the keyboard import java.util.Scanner; … Scanner in = new Scanner( System.in ); //wait until the user types something and // presses the return/enter key. in.nextLine();

Input/Output  An I/O example //declare variable(s) Scanner in = new Scanner( System.in ); //perform some i/o System.out.println( "hello. Press 'return' to continue." ); in.nextLine(); System.out.println( "That’s all. Press 'return' again." ); in.nextLine(); //finish up in.close();

Input/Output  Another I/O example //this program echoes what you type //declare variables Scanner in = new Scanner( System.in ); //perform some i/o System.out.print( "Enter something & press 'return' to continue." ); String what = in.nextLine(); System.out.print( "You typed: " + what + ". Press 'return' again." ); in.nextLine(); //finish up in.close(); String concatenation. Example of operator overloading.

String input  We’ve already discussed nextLine().  Reads an entire line (including blanks and/or tabs) up to but not including return/enter.  Additionally, we have next().  Skips leading whitespace (blanks) including return.  In effect, next() reads words including punctuation.  Skips consecutive blanks (if any).  Note: “blanks” include space, tab, and return/newline.

String input String s; Scanner in = new Scanner( System.in ); System.out.print( "Enter input: " ); s = in.nextLine(); You enter: Oh! That is terrible! Oh! That is terrible! What is the value of s?

String input String s; Scanner in = new Scanner( System.in ); System.out.print( "Enter input: " ); s = in.nextLine(); You enter: Oh! That is terrible! Oh! That is terrible! What is the value of s? s = “ Oh! That is terrible! ”

String input String s1, s2, s3; Scanner in = new Scanner( System.in ); System.out.print( "Enter input: " ); s1 = in.next (); s2 = in.next(); s3 = in.nextLine(); You enter: Oh! That is terrible! Oh! That is terrible! What are the values of s1, s2, and s3?

String input String s1, s2, s3; Scanner in = new Scanner( System.in ); System.out.print( "Enter input: " ); s1 = in.next (); s2 = in.next(); s3 = in.nextLine(); You enter: Oh! That is terrible! Oh! That is terrible! What are the values of s1, s2, and s3? s1 = “Oh!”s2 = “That”s3 = “ is terrible! ”

Reading Strings Note: When reading from the keyboard (not from a file), you must type in your string (or strings) and then you must hit.

String input summary 2 methods (associated w/ string input): 1.next() – Skips leading blanks, tabs, and newlines. – Reads a string of letters, digits, and underscores. 2.nextLine() – Doesn’t skip leading blanks and tabs. – reads an entire line up to but not including \n (newline)

Input/Output  Can we read other things (ints, doubles) besides strings?

Input/Output  Can we read other things (ints, doubles) besides strings? Yes. //calculate F = M A //get values System.out.print( "enter mass: " ); double mass = in.nextDouble(); System.out.print( "enter acceleration: " ); double acc = in.nextDouble(); //calculate result double force = mass * acc; System.out.println( "force = " + force );

Input/Output  Can we read other things (ints, doubles) besides strings? Yes. //calculate F = M A //get values System.out.print( "enter mass: " ); double mass = in.nextDouble(); System.out.print( "enter acceleration: " ); double acc = in.nextDouble(); //calculate result double force = mass * acc; System.out.println( "force = " + force ); Can you convert this to use ints instead of doubles?

Input/Output  Can we read other things (ints, doubles) besides strings? Yes. //calculate F=MA //get values System.out.print( "enter mass: " ); int mass = in.nextInt(); System.out.print( "enter acceleration: " ); int acc = in.nextInt(); //calculate result int force = mass * acc; System.out.println( "force = " + force ); Can you convert this to use ints instead of doubles?

Complete program “skeleton” or “template.” Java is an object oriented programming language. All code must be associated with an object. We declare an object as follows: /* introductory comment(s) */ import java.util.Scanner; // comment(s) about this class. public class Assignment5 { … //comment(s) about this method (function). public static void main ( String args[] ) { Scanner in = new Scanner( System.in ); System.out.println( "Computer is ready." ); … } //end main … } //end class Assignment5 definition