AP Java 10/4/2016

Learning Objectives Be able to use Java’s Swing class to make windows applications Be able to convert from String to int and double. Be able to use Math.random() and type casting to generate ranges of random numbers.

string a = "infinity"; 1. ) int b = a. length() - 4;. b = 2 string a = "infinity"; 1.) int b = a.length() - 4; b = 2.) int c = a.indexOf("ty") + b; c = 3.) boolean d = !a.equals("infinity"); d = 4.) String e = a.substring(4); e = 5.) String f = a.substring(1, 8); f = 6.) boolean g = a.equals("infInity"); g = 7.) int h = a.indexOf("z"); h = 8.) int i = a.length() - b/g; i = 9.) int j = a.substring(2); j = 10.) int k = a.indexOf("ini") * c; k =

Basic Input and Output using Java Swing.

GUI 101 with javax.swing // Fig. 3.17: Dialog1.java Look at java docs help files for JOptionPane to find out additional methods. // Fig. 3.17: Dialog1.java // Printing multiple lines in dialog box. import javax.swing.JOptionPane; public class Dialog1 { public static void main( String args[] ) // display a dialog with the message JOptionPane.showMessageDialog( null, "Welcome\nto\nJava" ); } // end main } // end class Dialog1

Input with swing // Fig. 3.18: NameDialog.java // Basic input with a dialog box. import javax.swing.JOptionPane; public class NameDialog { public static void main( String args[] ) // prompt user to enter name String name = JOptionPane.showInputDialog( "What is your name?" ); // create the message String message = String.format( "Welcome, %s, to Java Programming!", name ); // display the message to welcome the user by name JOptionPane.showMessageDialog( null, message ); } // end main } // end class NameDialog Input with swing

Swing input stuff It only enters a String, not a double or int. So to enter numbers you will need to convert them to integers or doubles To convert a String into an integer. int answer=Integer.parseInt(name); To convert to a double: double answer=Double.parseDouble(name);

String For int, import javax.swing.JOptionPane; public class NameDialog { public static void main( String [] args) // prompt user to enter name String name = JOptionPane.showInputDialog( "What is your name?" ); //Prompt for the age String ageString =JOptionPane.showInputDialog( "What is your age?" ); int age = Integer.parseInt(ageString); // create the message String message = String.format( "Welcome, %s, to Java Programming! \n %d", name, age ); // display the message to welcome the user by name JOptionPane.showMessageDialog( null, message ); } // end main } // end class NameDialog String For int, Use %f for double

Swing Program Tree height calculator: Resisting Change Input the distance you are from a tree and the angle you look up to the top of the tree. Output: The height of the tree. Calculation: tree height = the height of your eyes + (Distance from the tree) * tan(angle) Look up the Math.tan() method to determine if the angle is in degrees or radians. Push: Research to find out how to use this information to estimate the number of ‘board-foot’ volume of the standing tree. Will you need any other information? Resisting Change Input: The resistance in Ohms of two resistors wired in parallel (r1 and r2). Output: The net resistance. NetResistance = r1*r2 / (r1 + r2) Push: Be able to find the resistance given three resisters connected in parallel. Push: Be able to find the resistance of n resistors connected in parallel. Let the user enter the number of resisters.

public static void main( String [] args) int roll; What do you think this program does? Type it in BlueJ and test it. public class Rolling { public static void main( String [] args) int roll; for (int count = 1; count < 10; count++) roll = (int)(6*Math.random())+1; System.out.print(roll); } } // end main

Math.random(); Returns a double value in the range 0<=Math.random() < 1. You can change its type from double to int by type casting. roll = (int)(6*Math.random())+1;

Random Practice Describe the range of random values generated from the following. int one = (int)(6*Math.random()) + 1; int roll = (int)(10*Math.random()) + 6; int roll = (int)(20*Math.random()) - 3; int roll = 2* ((int)(6*Math.random())) + 10; int roll = 2* ((int)(6*Math.random())) + 1; double roll = Math.random() + 1; double roll = 6*Math.random() + 1;

More Random Practice Write the code needed to generate the following ranges of random numbers. 2 to 7 -5 to 5 50 to 70 10 to 26 even A pair of 20 sided dice Double values from 1 to 5 Double values from 4 to 10 Double values from -5 to 5

Use Swing to create a GUI for this program. Program options Use Swing to create a GUI for this program. Flip a coin 100 times, show the total number of heads and tails AND which occurred the most often. Roll a pair of 6 sided dice 100 times. Find out which occurs most often, 3 or 11. Show how often each of these rolls occur and which occurs most often. Widget walk. Put a widget (any graphic, circle, dot,…) on the screen. Have it move randomly for 100 steps. Push: Look up JOptionPane in Java Docs and incorporate a method not described in today’s presentation.