Repetition - Business Application Programming - Lecture Slides, Slides of Applications of Computer Sciences

Download Repetition - Business Application Programming - Lecture Slides and more Slides Applications of Computer Sciences in PDF only on Docsity!

Chapter 6:

Repetition

Object-Oriented Program

Development Using Java: A

Class-Centered Approach

Objectives

• Basic Loop Structures
• The while Statement
• Interactive while Loops
• The for Statement
• The do-while Statement
• Recursion

Basic Loop Structures

• Repetition statements:
  • Provide the capability to type a set of instructions once
  • Have instructions repeated continuously
  • Until some preset condition is met

Basic Loop Structures

(continued)

• Elements required for repetition:
  • Repetition statement
  • Condition that must be evaluated
  • Statement that initially sets the condition
  • Statement within repeating section of code that allows condition to become false

Pretest and Posttest Loops

• Pretest loop
  • The condition being tested is evaluated at the beginning of the repeating section of code - If the condition is true the executable statements within the loop are executed - If the initial value of the condition is false the executable statements within the loop are never executed at all
  • Also referred to as entrance controlled loops

Pretest and Posttest Loops

(continued)

• Posttest loop
  • A loop that evaluates a condition at the end of a repeating section of code
  • Always executes loop statements at least once before the condition is tested
  • The do-while construct is an example of a posttest loop

Fixed-Count Versus Variable-

Condition Loops

• Fixed-count loop
  • The condition is used to keep track of how many repetitions have occurred
  • All of Java’s repetition statements can be used
• Variable-condition loop
  • The tested condition depends on a variable that can change interactively with each pass through the loop
  • All of Java’s repetition statements can be used

Evaluating a while Statement

• Test condition
• If condition has nonzero (true) value
  • Execute statement following parentheses
  • Go back to step 1
• Else
  • Exit the while statement

Interactive while Loops

• Combining interactive data entry with the repetition capabilities of while statements produces adaptable and powerful programs
• A user-entered value is used in a conditional statement

Sentinels

• Sentinels:
  • Data values that signal either the start or end of data series
  • Must be selected so as not to conflict with legitimate data values

The break and continue

Statements (continued)

• continue statement
  • Applies only to loops created with:
    • while
    • do-while
    • for
  • When encountered in a loop the next iteration of the loop begins immediately
  • Not often used in practice

The null Statement

• Semicolon with nothing preceding it
• Do-nothing statement
  • Used where statement is syntactically required but no action is called for