Chapter 5 - Making Decisions

MIS 3370: Information Systems Development Tools 1

Instructor Information

Professor: Dr. Barry Ingram
Department: Decision and Information Sciences
College: Bauer College of Business
University: University of Houston

Chapter 5: Making Decisions

Planning Decision-Making Logic

Pseudocode
- Use paper and a pencil.
- Plan a program’s logic by writing plain English statements.
- Accomplish important steps in a given task.
- Use everyday language.
Flowchart
- Visual representation of steps in diagram form.
- A series of shapes connected by arrows.
- Programmers use various shapes for different tasks:
- Rectangle for any unconditional step.
- Diamond for any decision.

Planning Decision-Making Logic Structures

Sequence Structure
- One step follows another unconditionally.
- Cannot branch away or skip a step.
Decision Structure
- Involves choosing among alternative courses of action.
- Based on some value within a program.

Flowchart Examples

Figure 5-1: Flowchart of a series of sequential steps.
Figure 5-2: Flowchart including a decision.
- Note: All computer decisions are yes-or-no decisions.
- Boolean values represent true and false values, used in every computer decision.

The if and if…else Structures

if Statement
- Sometimes called a single-alternative decision.
- Simplest statement to make a decision.
- Contains a Boolean expression within parentheses.
- No space between the keyword if and the opening parenthesis.
- Execution continues with the next independent statement.
- Use a double equal sign (==) to determine equivalency.
- Example:
  java if (discount < .50) { discount = .50f; }
- This compares the discount to .50, and if smaller, sets discount to 50%.

Coding Example: Project Setup

Create a project/package in NetBeans for Chapter 5.
Copy Orders.java and CustOrders.java.
Create a class called UseConditions.
Write code that sets an integer called quizScore to 26.
Write a conditional statement:

   if (quizScore > 25) {
       System.out.println("I made a 100% on my quiz!");
   }

The Role of Semicolons in if Statements

Pitfall: Misplacing a Semicolon
- There should be no semicolon at the end of the first line of the if statement; doing so creates an empty statement, causing execution to continue with the next independent statement.

Using the Assignment Operator vs. Equivalency Operator

Attempt to determine equivalency using a single equal sign (=) is illegal.
- Correct usage requires double equal sign (==).

Using Boolean Values as Conditional Statements

Example code change to useConditions.java:

   myQuiz += 19;
   boolean isPerfectScore = (myQuiz == 45);
   if (isPerfectScore) {
       System.out.println("I made a perfect score on my quiz");
   }

Attempting to Compare Objects

Use standard relational operators to compare values of primitive data types—not objects.
- Use equals and not equals comparisons (== and !=) to compare memory addresses rather than values (e.g., firstStudent > secondStudent).

The if…else Structure

Single-alternative if: Acts on one alternative.
Dual-alternative if: Two possible courses of action
- if...else statement: Executes different actions based on the evaluation of a Boolean expression.

Example of if…else Code

if (quizScore == 10) {
    System.out.println("The score is perfect");
} else {
    System.out.println("No, it's not");
}

In-Class Assignment Example

In UseConditions, write a dual alternative that sets an integer variable of choice to 0.
Print out white the message depending on myChoice:
- If myChoice is 0: "I made my choice".
- Else: "I have not made my choice".
Make these changes in useConditions.java.

Using Multiple Statements in if Conditions

To execute more than one statement, use a pair of curly braces {}.
Place dependent statements within this block, and ensure the correct placement of curly braces to avoid logical errors.
Example demonstrating issues with indentation/missing braces included.

Nesting if and if…else Statements

Nested if statements: Utilize when multiple conditions must be satisfied before performing an action.

Making Accurate and Efficient Decisions

Range Check: A series of if statements verifying if a value lies within a specified range.
Strategically order conditions for efficient evaluation.
Example:

if (score >= 90) {
    System.out.print("A");
} else if (score >= 80) {
    System.out.print("B");
} // etc.

Commission Rate Decision Example

Example illustrating commission rates set based on thresholds:

if(saleAmount < LOW_LIM) {
    commissionRate = LOW_RATE;
} else if(saleAmount < MED_LIM) {
    commissionRate = MED_RATE;
} else {
    commissionRate = HIGH_RATE;
}

Logical Operators Overview

Logical NOT (!): Negates any Boolean expression.
Logical AND (&&): Requires both conditions to be true.
Logical OR (||): Requires at least one condition to be true.

switch Statement Explained

An alternative to nested if statements.
Compares a single variable against a series of integer, character, or string values.
Syntax includes: switch, case, break, and default keywords.

Example of switch Statement

switch(day) {
    case "Monday":
        System.out.println("Reserve room for Friday meeting");
        break;
    default:
        System.out.println("Invalid day");
}

Operator Precedence

Indicates how expressions are evaluated.
Includes conventions like using parentheses to clarify intentions.
Example with incorrect vs correct assignment of extra premiums using AND/OR operators.

In-Class Assignment for Discounts

Update logic in orders.java to ask for percentage discount input instead of a multiplier.
Additional tasks include customer type handling and applying customer-specific discounts using a case statement, with final output generation.

Example of Final Receipt Output

A well-formatted receipt showcasing customer type, order number, total costs, and discounts applicable.