Download presentation

Presentation is loading. Please wait.

Published byEsther Michaels Modified over 2 years ago

1
Methods

2
Read two numbers, price and paid (via JOptiondialog) Calculate change; s = JOptionPane.showInputDialog("Enter price”); Double price = Double.parseDouble(s); s = JOptionPane.showInputDialog("Enter paid amount”); Double paid = Double.parseDouble(s); Double change = paid – price; JOptionPane.showMessageDialog(null, “change is: “ + change);

3
Is this program segment correct What are the rules? – s may have only digits and at most one decimal point. s = JOptionPane.showInputDialog("Enter price”); Double price = Double.parseDouble(s); s = JOptionPane.showInputDialog("Enter paid amount”); Double paid = Double.parseDouble(s); Double change = paid – price; JOptionPane.showMessageDialog(null, “change is: “ + change);

4
Is every character of s a digit? – Check the first character If it is not a digit – Stop – not a number If it is a digit – So far so good Check the next character the same way … How many times do you do this for? – One time for each character How many characters are in s? – s.length() characters

5
Is every character of s a digit? 1.Start from the first character of s int i=0 2.Check the next character of s if (Character.isDigit(s.charAt(i)) 3.Pick the next character of s i=i+1; 4.Repeat steps 2-3 until you check the last character Repeat as long as i < s.length() for (int i=initialValue; condition; step) { } for (int i=0; i < s.length(); i=i+1) { }

6
Is every character of s a digit? String s1 = JOptionPane.showInputDialog("Enter price”); Double price = Double.parseDouble(s1); for (int i=0; i < s1.length(); i=i+1) if (!Character.isDigit(s1.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } String s2 = JOptionPane.showInputDialog("Enter paid amount”); Double paid = Double.parseDouble(s2); Double change = paid – price; JOptionPane.showMessageDialog(null, “change is: “ + change);

7
Is every character of s a digit? String s1 = JOptionPane.showInputDialog("Enter price”); Double price = Double.parseDouble(s1); for (int i=0; i < s1.length(); i=i+1) if (!Character.isDigit(s1.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } String s2 = JOptionPane.showInputDialog("Enter paid amount”); Double paid = Double.parseDouble(s2); for (int i=0; i < s2.length(); i=i+1) if (!Character.isDigit(s2.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } Double change = paid – price; JOptionPane.showMessageDialog(null, “change is: “ + change); Same code!! What if we factor out the common code, give it a name and refer to it by its name when needed?

8
Methods Common and frequently used that perform a well-defined task are factored out into program segments called methods for (int i=0; i < s.length(); i=i+1) if (!Character.isDigit(s.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } Check(String s)

9
Methods void check (String s) { for (int i=0; i < s.length(); i=i+1) if (!Character.isDigit(s.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } String s1 = JOptionPane.showInputDialog("Enter price”); check(s1); Double price = Double.parseDouble(s1); String s2 = JOptionPane.showInputDialog("Enter paid amount”); check(s2); Double paid = Double.parseDouble(s2); Double change = paid – price; JOptionPane.showMessageDialog(null, “change is: “ + change);

10
Methods void check (String s) { for (int i=0; i < s.length(); i=i+1) if (!Character.isDigit(s.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } String s1=“24.87”; Check(s1); 24.87 String s2=“32.8X7”; Check(s2); 32.8x7

11
Is there at most at one decimal point? 1.Start from the first character of s int i=0 boolean decimalPoint=false; 2.Check the next character of s if (s.charAt(i) == '. ' ) Check if this is the first decimal point If (!decimalPoint) Remember that we have seen a decimalpoint decimalPoint=true; 3.Repeat steps 2-3 until you check the last character Repeat as long as i < s.length()

12
Is there at most at one decimal point? void check (String s) { boolean decimalPoint=false; for (int i=0; i < s.length(); i=i+1) if (s.charAt(i) == '. ') if (!decimalPoint) decimalPoint=true; else { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); }

13
Is every character a digit and Is there at most at one decimal point? void check (String s) { boolean decimalPoint=false; for (int i=0; i < s.length(); i=i+1) if (s.charAt(i) == '. ') if (!decimalPoint) decimalPoint=true; else { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } void check (String s) { for (int i=0; i < s.length(); i=i+1) if (!Character.isDigit(s.charAt(i))) { JOptionPane.showMessageDialog(null, "You must enter an integer value"); System.exit(0); } Combine the two check methods

14
Where do we place methods? /** * @param args the command line arguments */ public static void main(String[] args) { // TODO code application logic here ….. } public static void check(String s) { ….. } public class Assignment1 { }

Similar presentations

OK

Introduction to Computers and Programming Lecture 3: Variables and Input Professor: Evan Korth New York University.

Introduction to Computers and Programming Lecture 3: Variables and Input Professor: Evan Korth New York University.

© 2017 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on nitrogen cycle and nitrogen fixation is carried Ppt on online mobile shopping Ppt on sports day outfits Ppt on property management system Ppt on charles dickens and his life Download ppt on pulse code modulation notes Ppt on opposites in hindi Ppt on social media addiction Presentations ppt online reader Ppt on instrument landing system cost