Java Programming Chapter 2, Slides of Java Programming

Download Java Programming Chapter 2 and more Slides Java Programming in PDF only on Docsity!

Java Programming

Sixth Edition

Chapter 2

Using Data

Objectives

• (^) Use constants and variables
• (^) Use integer data type
• (^) Use the boolean data type
• (^) Use floating-point data types
• (^) Use the char data type

Using Constants and Variables

• (^) Constant
  • (^) Cannot be changed while program is running
• (^) Literal constant
  • (^) Value taken literally at each use
• (^) Numeric constant
  • (^) Opposed to a literal constant
• (^) Unnamed constant
  • (^) No identifier is associated with it

Using Constants and Variables

(cont'd.)

• (^) Variable
  • (^) Named memory location
  • (^) Use to store value
  • (^) Can hold only one value at a time
  • (^) Value can change
• (^) Data type
  • (^) Type of data that can be stored
  • (^) How much memory item occupies
  • (^) What types of operations can be performed on data

Using Constants and Variables

(cont'd.)

Declaring Variables

• (^) Name variables
  • (^) Using naming rules for legal class identifiers
• (^) Variable declaration
  • (^) Statement that reserves named memory location
  • (^) Includes:
    • (^) Data type
    • (^) Identifier
    • (^) Optional assignment operator and assigned value
    • (^) Ending semicolon

Declaring Variables (cont'd.)

• (^) Declare multiple variables of same type in separate

statements on different lines

int myAge = 25; int yourAge = 19;

• (^) Declare variables of different types
  • (^) Must use separate statement for each type

Declaring Named Constants

• (^) Named constant
  • (^) Should not change during program execution
  • (^) Has data type, name, and value
  • (^) Data type preceded by keyword final
  • (^) Can be assigned a value only once
  • (^) Conventionally given identifiers using all uppercase letters

The Scope of Variables and Constants

• (^) Scope
  • (^) Area in which it is visible to a program and in which you can refer to it using its simple identifier
• (^) A variable or constant is in scope from the point it

is declared

• (^) Until the end of the block of code in which the declaration lies

Pitfall: Forgetting That a Variable

Holds One Value at a Time

• (^) Each constant can hold only one value
  • (^) For duration of program
• (^) Switch values of two variables
  • (^) Use third variable

Learning About Integer Data Types

(cont'd.)

Using the boolean Data Type

• (^) Boolean logic
  • (^) Based on true-or-false comparisons
• (^) boolean variable
  • (^) Can hold only one of two values
  • (^) true or false

boolean isItPayday = false;

• (^) Relational operator (comparison operator)
  • (^) Compares two items

Learning About Floating-Point Data

Types

• (^) Floating-point number
  • (^) Contains decimal positions
• (^) Floating-point data types
  • (^) float
  • (^) double
• (^) Significant digits
  • (^) Refers to mathematical accuracy

Learning About Floating-Point Data

Types (cont'd.)