Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Lecture 8 Review (Methods of Math class) int abs( int num ) double sqrt( double num ) double pow( double num, double power ) Data type of the result Method parameters Please take a look more Math methods at http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Math.html#method_summary Example 2.25 double area = 2.25; double value2 = Math.sqrt( area ); System.out.println( “value2 is “ + value2); value2 is 1.5 Example pow method takes two variables (radius)2 double PI = 3.14; double radius = 1.5; double area = PI * Math.pow( radius, 2 ); System.out.println( “Area is “ + area); More Methods of Math class Please take a look more Math methods at http://java.sun.com/j2se/1.4.2/docs/api/java/lang/Math.html#method_sum mary Today’s topic • Java application – Let’s write codes for calculator application • Constant variable • Talk about project 1 Write Create Programmer (who we are) Java Program Java Application Use User User Interface • There are three actors – Programmer: who writes codes for applications – Computer: who runs applications – User: who uses applications • Programmers have to consider two interactions – Programmer Computer – Computer User – So, programmers write codes for user interface • how users interacts with applications For example Programmer (who we are) Application User For example Programmer (who we are) User interface Application should direct users User Example (MyCalculator.java) Please create a new folder, named Example Please download “acm.jar” file into the folder at http://www.cs.umb.edu/~chonho/teaching/2007/files/ In Dr.Java, add acm.jar file for extra classpath in preference window from [edit] Create a new file, named MyCalculator.java and save it into the folder MyCalculator.java Let’s start with class header and main method public class MyCalculator { public static void main(String[] argv) { } } MyCalculator.java (1) /* * File name: MyCalculator.java * -------------------------* This program runs as a Java application without using the acm.program package. */ Comment import acm.io.*; import java.awt.*; import javax.swing.*; public class MyCalculator { Single line: // Multiple lines: /* … */ Class name It should be same as file name MyCalculator.java (2) public class MyCalculator { public static void main(String[] argv) { Frame title JFrame frame = new JFrame(“My Calculator"); IOConsole console = new IOConsole(); frame.getContentPane().add(BorderLayout.CENTER, console); Create classes frame.setSize(500, JFrame 300); class of JFrame class IOConsole Methods class frame.setVisible(true); MyCalculator.java (3) int num1, num2, total; console.println( "This program adds two numbers.” ); println() num1 = console.readInt( “Enter num1: “ ); same as System.out.println() num2 = console.readInt( “Enter num2: “ ); print out message in console total = num1 +but, num2; } } readInt(it )receives method 1 string parameter ask users to enter antotal integer console.println("The total is " + + ".");number it receives 1 string parameter Constant variable • Constant variable is static, and its value does not change within entire programs. – You can deal with it as regular variable • Declaration of constant variable – Regular variable double average; – Constant static final double PI = 3.14; Exercise • 1. Mile to Kilometer conversion • 2. Fahrenheit to Celsius conversion • 3. Circle circumference and area Exercise 1 • Mile to Kilometer conversion 1 Mile is 1.6 Kilometer Create a calculator application to convert unit from Mile to Kilometer - Ask an user to enter one number in mile - Calculate the unit conversion - Print out the result in Kilometer for the user. public class MyCalculator { public static void main(String[] argv) { JFrame frame = new JFrame(“My Calculator"); IOConsole console = new IOConsole(); frame.getContentPane().add(BorderLayout.CENTER, console); frame.setSize(500, 300); frame.setVisible(true); double mile, kilo; console.println( "This program converts mile to kilometer.” ); mile = console.readDouble( “Enter number in mile: “ ); kilo = 1.6 * mile; console.println( mile + “ mile is " + kilo + “ kilometer"); } } Constant Variable double mile, kilo; console.println( "This program converts mile to kilometer.” ); mile = console.readDouble( “Enter number in mile: “ ); kilo = 1.6 * mile; console.println( mile + “ mile is " + kilo + “ kilometer"); static final double MileToKilometer = 1.6; Add this line as an attribute in a class double mile, kilo; console.println( "This program converts mile to kilometer.” ); mile = console.readDouble( “Enter number in mile: “ ); kilo = MileToKilometer * mile; console.println( mile + “ mile is " + kilo + “ kilometer"); public class MyCalculator { static final double MileToKilometer = 1.6; public static void main(String[] argv) { JFrame frame = new JFrame(“My Calculator"); IOConsole console = new IOConsole(); frame.getContentPane().add(BorderLayout.CENTER, console); frame.setSize(500, 300); frame.setVisible(true); console.println( "This program converts mile to kilometer.” ); double mile = console.readDouble( “Enter number in mile: “ ); double kilo = MileToKilometer * mile; console.println( mile + “ mile is " + kilo + “ kilometer"); } } Exercise 2 (comment out previous one) • Fahrenheit Tf to Celsius Tc conversion Conversion formula Tc = (5 / 9) * (Tf – 32) Create a calculator application to convert unit from degree Fahrenheit to Celsius - Ask an user to enter number in Tf - Calculate the unit conversion - Print out the result in Tc for the user. Exercise 3 (comment out previous one) • Circle circumference and area PI = 3.14 circumference = 2 * PI * radius area = PI * (radius)2 radius Create a calculator application to compute the circumference and area of circle - Ask an user to enter number for radius of circle - Calculate the circumference and are - Print out both results for the user. Challenge • If you want to do calculation twice or more without closing windows, then you can use loop to ask users for entering new numbers. console.println( "This program adds two numbers.” ); for( int i=0; i<5; i++) { num1 = console.readInt( “Enter num1: “ ); num2 = console.readInt( “Enter num2: “ ); total = num1 + num2; console.println("The total is " + total + "."); }