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CIS 260: App Dev I
Programs and Programming

Program
 A sequence of steps designed to accomplish a task

Program design
 A detailed _____ for implementing a program

Programming
 The process of implementing a program design

Application program
 A stand-alone computer program that is applied to a
real-world problem
2
The Java Programming Language

Programming language
 The ________ used to create valid program
statements

Syntax
 The symbols, words, and rules of a programming
language

A simple Java program
public class Welcome
{
public static void main( String[] args )
{
System.out.println( "Welcome to Java Programming“ );
}
}
3
The Java Syntax

Tokens
 Special symbols, word symbols, and __________ of a language

Special symbol
 One or more characters w/ special meaning
 Examples: +, -, *, /, <, …

Word symbols
 Reserved word (___________)
 Examples: int, static, return, true, …

Identifier
 Predefined or user-defined names of things
 Examples: print, totalCost, …
4
Data Types

Data type
 A classification of data according to legal values and
legal operations on those values

Primitive data types in Java
primitive
character
numeric
integral
char
byte
short
int
logical
floating-point
long
float
double
boolean
5
Details on Selected Data Types

char
 Examples: ‘A’, ‘a’, ‘$’, ‘&’, ‘ ’ , …
 Unicode 65 is ‘A’ and Unicode 43 is ‘+’

int
 Non-decimal (whole number) values
 Range of values: -2147483648 to 2147483647
 Examples: 24, -117, 34082, 0 , …

double
 Decimal values with up to 15 decimal places (double precision)
 Range of values: -1.7 x 10308 to 1.7 x 10308
 Examples: 14.75 , -.00053 , -289038432.8993,
-5.3E-4

boolean
 Logical values
 Examples: true, ___________
6
Arithmetic Operators

Possible arithmetic operators for integral and floatingpoint data types:
 +, -, *, /, % (remainder upon division)

Examples








8+7 yields 15
6-15 yields -9
6*8 yields 48
6*8.0 yields 48.0
15/4 yields _____
15/4.0 yields 3.75
15%7 yields 1
15.2%7 yields _____
7
Order of Precedence





*, /, and % have the same precedence
+ and – have the same precedence, but lower
than *, /, and %
Operations with the same precedence are
performed from left to right
()’s can be used to override normal
precedence
Examples
 4 + 8 / 2 % 3 yields ____
 (4 + 8 / 2) % 3 yields ____
8
Expressions

Integral expressions
 All operands are integers or integer types
 Example: (apples + oranges) * 2

Floating-point expressions
 All operands are floating-points or floating-point types
 Example: totalCost * .05

Mixed expressions
 Operands are of different types
 Examples:
• 2*5/mpg yields ______ if mpg is 4.0 (double)
• cost/2+(7-10.0) yields _______ if cost is 3 (int)
9
Type Casting

Implicit type coercion
 Occurs automatically with mixed expressions
 15/4.0 automatically becomes 15.0/4.0

Explicit type conversion
 Also called type _________
 Converts a result to a desired data type
 Examples
• (double) 15/3 yields ______
• (int) (16/3.0)+2*8%5 yields ______
• (int) 16/number + 7 yields _____ if number is 2.0
• (char) 65 yields ______
10
The class String





A string is a sequence of 0 or more characters
enclosed in double ________ (e.g., “Joe” )
In Java, a String is not a primitive data type
A String with no characters is called a _____
string (“”)
The length of a String is its number of
___________
The position of a character in a String starts
with 0 for the first, 1 for the second, …
11
Parsing Numeric Strings



In Java, input can only be received as a string
or character
A string with only integers or decimal numbers is
called a ________ string (e.g. “78.3”, “.0038”,
“17”)
To convert a numeric string to an actual number
in Java
 Integer.parseInt(“17”) yields ____
 Double.parseDouble(“78.3”) yields ____
 Integer.parseInt(numInput) yields ____
12
Variables and Named Constants

How to store program data in main memory:
 Write a statement to ___________ memory
 Write a statement to put data in memory location

Data that may change during program execution
are stored in a ___________.
 int hoursWorked; // allocates memory
 hoursWorked = 45; // puts data in
 int overtimeHours = 5; // does both

Data that should not change during program
execution are stored in a named ___________.
 final double PAY_RATE = 7.50;

Variables and constants are just __________
locations.
13
Assignment Statements

_______ variables in Java (allocate memory):
 double cost;
 String firstName, lastName;
 int i, j, k;

________ variables in Java (store in memory):
 cost = 19.95;
 firstName = “Richard”;
 i = i + 1; // get i, add 1, store in i


The “=“ is an _________ operator, not “equals”.
It literally means “is assigned the value”.
Assign a new value to an existing variable:
 cost = materiaCost + laborCost;
14
Input: The Scanner Class


Java is a pure OO language and uses its own
___________ classes, objects, and methods.
The Scanner input stream class (new in 5.0):






static Scanner console = new Scanner( System.in );
console.nextInt() // gets next item as an integer
console.nextDouble() // gets next item as a double
console.next() // gets next item as a String
console.nextLine() // gets everything to end of line
To read a single character:
 char aCharacter;
 aCharacter = console.next().charAt(0);

To convert string data to numeric data:
 double price;
 price = Double.parseDouble( console.nextDouble() ); 15
Input: The JOptionPane Class



GUIs can be used for program input and output.
Using GUIs requires an _________ statement.
The following statement (must be the first
statement) imports the JOptionPane class:
 import javax.swing.JOptionPane;

This statement uses the showInputDialog
method to get _________ input:
 name = JOptionPane.showInputDialog
( “Enter your name.” );

This statement uses the showMessageDialog
method to display output:
 JOptionPane.showMessageDialog( null,
outputMessage );
16
Increment and Decrement

The following type of statement is used a lot:
 count = count + 1;
 It means “get the value in count, add 1 to it, assign that to count”
 A shortcut in Java: count++; or ++count;

Increment and decrement operators have prefix and
_______ forms.
 The prefix form is evaluated before the expression is evaluated.
 The postfix form is evaluated ______ the expression is
evaluated.

Example:
int
c =
c =
c =
a
2
a
a
=
+
+
+
0, b =
(++a);
(b++);
(++b);
0,
//
//
//
c =
___
___
___
0;
will be stored in c
will be stored in c
will be stored in c
17
Using the String Class

A String object usually consists of one or more
__________.
String title = “War and Peace”;

The following shows an empty String and a null
String:
 String code = “”; // has memory address
 String inputValue = null; // no address

_______ sequences use the \ to create new
lines, tabs, or special characters.
“\”Bud\”\tSmith \n Rick\tAnkiel” 
“Bud” Smith
Rick
Ankiel
18
String Class Methods/Joining

A method of a class is called using the object
name, a ____, and the method name (with
arguments).
String choice=“X”;
if (choice.equals(“x”)) // returns false

How to join (____________) String objects:
String title = “War and Peace”;
double price = 14.95;
String message = “Title: ” + title + “\n”
+ “Price: ” + price;

Note the code is written to enhance readability.
19
Output
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

In Java, the standard output object is
__________ with methods print and _______.
print leaves the cursor at the end of the current
line while println moves it to the next line.
System.out.println(‘q’);// displays q
System.out.println(“Joe”);// displays Joe
Escape sequence \n is for a new _____, \t is
for a _____.
Example
String name = “Joe”;
System.out.println(“My name is \n” + name + “.”);
20
Packages and import

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
In Java, a package is a collection of related
________.
A class is a section of Java code in a file that
contains methods and data definitions.
A method is a set of instructions to accomplish a
specific _____.
The package _________ contains classes for
program input and output.
To make all classes in java.io available in your
program you need the statement
________________ at the very beginning.
21
Java Application Programs


Your Java application program must contain at
least one class and one of those classes must
have a method called ______.
The method main has two parts:
 The heading:
• public static void main(String [] args)
– public means main is accessible to other classes
– static means main isn’t directly related to objects
– void means main will not return data
 The body
• Enclosed in { } ’s
• Contains declaration statements: int myAge, yourAge;
• Contains executable statements: myAge = 50;
22
Programming Style and Form

________ rules must be followed. For example,
 You must place a “;” at the end of each program
statement
 { } ‘s must always occur in pairs

Form and style:
 Write just one statement per line
 Indent lines for readability (as shown in examples)
 Add important _____________ using // and /*…*/
• Always begin a program with comments for the program
name, the programmer, the date, and the program purpose
 Naming variables (hourlyWage), constants (TAX_RATE)
 Provide prompt text for input
23
 Provide good explanation for input and output
//A properly formatted Java program.
import java.util.Scanner;
A Java Application Program
public class IntegerNameHeight
{
static Scanner console = new Scanner( System.in );
public static void main( String[] args )
{
// preparation
int num;
double height;
String name;
// input
System.out.print("Enter an integer: ");
System.out.flush();
num = console.nextInt();
System.out.println();
System.out.print( "Enter the first name: “ );
System.out.flush();
name = console.next();
System.out.println();
System.out.print( "Enter the height: “ );
System.out.flush();
height = console.nextDouble();
// output
System.out.println();
System.out.println( "num: " + num );
System.out.println( "Name: " + name );
System.out.println( "Height: " + height );
}
}