CIS 120 CHAPTER 4

PROBLEM SOLVING AND CONTROL STRUCTURES I

1. Terms

· algorithm: finite set of instructions clearly written which eventually terminate producing desired output.

· Pseudocode: English-like statements that resemble programming language syntax. Intention is to make conversion to actual code easier.

· Step-wise refinement: iterative process of decomposition of abstract problem

· Abstraction: looking at the problem as a whole, sum of its part, rather than as individual components.

2. Control Structures

· Sequence

· Selection

· Repetition

3. Flow Chart Symbols for the control structures.

4. Selection

if

if else

multiple selection

?: (conditional operator, {ternary (3 operands) operator})

Boolean expression?: true action : false action;

System.out.println(grade >= 60 ?: “Passed” : “Failed”);

Dangling else problem: occurs in a nested if statement where the outer if has an else and the inner if does not. The else component binds with the closest if.

5. While structure

Example 1

int product = 2;

while (product <= 1000)

product = 2 * product;

Example 2: Counter controlled

String grade;

int total = 0;

int gradeValue;

int counter = 1;

while (counter <= 10)

{ grade = JOptionPaneshowInputDialog(“Enter next grade”);

gradeValue = Integer.parseInt(grade);

total += gradeValue;

counter ++;

}

Example 3: Sentinel controlled and priming read

String grade;

int total = 0;

int gradeValue;

grade = JOptionPaneshowInputDialog(“Enter next grade”);

gradeValue = Integer.parseInt(grade);

while (gradeValue != -1)

{ total += gradeValue;

grade = JOptionPaneshowInputDialog(“Enter next grade”);

gradeValue = Integer.parseInt(grade);

}

6. DecimatFormal class

DecimatFormal twoDigits;

twoDigits = new DecimalFormat(“0.00”); //at least 1 digit to left of decimal point,

// exactly 2 digits to the right.

System.out.println(“Average grade = “ + twoDigits(average));

7. Note—Study algorithms and problem solving strategies discussed in Chapter 4.

8. See Tables in text:

· Figure 4.12: Arithmetic assignment operators

· Figure 4.13: Increment and decrement operators

· Figure 4.15: Precedence table

· Figure 4.16: Java primitive data types (8)—byte, char, short, int, long, float, double, Boolean