Using Data Within A Program

1
Using Data Within A Program

• Chapter 2
• Dr. James Jiang

Data Within a Program
2
Variables and Constants

• Literal constant
• System.out.println(459)
• Variables ? named memory locations
• System.out.println(ovenTemperature)
• Primitive data types
• boolean float
• byte int
• char long
• double short

3
Variable Declaration

• Identify the type of data
• Variable name begin with lowercase letter to
  distinguish variable from class
• Initial assigned value (optional)
• Semi-colon

4
Variable Declarations

• int myAge 25
• int yourAge 20
• OR
• int myAge 25, yourAge 20
• int myAge, yourAge
• double mySalary, yourSalary

5
int

• Integers or whole numbers
• -2,147,483,648 to 2,147,483,647
• byte, short, long are variations of the integer
  type
• When assigning values, dont type commas (only
  numbers and/or signs)

6
Printing Compound Phrases

• System.out.print(The int is )
• System.out.println(oneInt)
• OR
• System.out.println(The int is oneInt)

7
Arithmetic Operators

• - /

• Use modulus () only with integers
• Use , -, , / with floating-point data and
  integers
• Operator precedence - order of evaluation of
  mathematical expression

8
Boolean Data Type

• Values true, false
• boolean isItPayDay false
• boolean areYouBroke true
• Use is or are as part of variable name for
  identification purposes

9
Comparison Operators

• lt Less than
• gt Greater than
• Equal to
• lt Less than or equal to
• gt Greater than or equal to
• ! Not equal to

boolean overtime (hours gt 40) boolean
highTaxBracket (income gt 100000)
10
Floating-Point Data Types

• Contain decimal positions
• float - 7 significant digits of accuracy
• double - 15 significant digits of accuracy
• double is the default
• To store as float
• float pocketChange 4.87F

11
Numeric Type Conversion

• Arithmetic operations with operands of unlike
  types
• Java automatically (implicitly) converts operands
  to unifying type
• double
• float
• long
• int
• short
• byte

12
Numeric Type Conversion

• Example
• int hoursWorked 37
• double payRate 6.73
• grossPay hoursWorked payRate
• grossPay must be a double

13
Overriding the Unifying Type

• Use type casting
• Place desired result type in parentheses
• double bankBalance 189.66
• float weeklyBudget (float) bankBalance / 4

14
char Data Type

• Holds any single character
• Place within single quotation marks
• Store a string of characters using the String
  data structure
• To store nonprinting characters using an escape
  sequence
• char aBackspaceChar \b
• char aLinefeedChar \n
• Unicode - 16-bit character coding scheme

15
Exercise 2-13 (p.52)

• //Name James Jiang
• public class Interest
• private double principle 1000, rate 0.05
• private double futureAmount
• private int month 6
• public static void main (String args)
• futureAmount principle (1 rate
  month / 12)
• System.out.println (The future amount
  is futureAmount)