Section 5.7 Worked Example: While Loops - Sentinel
Subgoals for Evaluating a Loop.
- Diagram which statements go together.
-
Define and initialize variables
- Determine the start condition.
- Determine the update condition.
- Determine the termination condition.
- Determine body that is repeated.
-
Trace the loop.
- For every iteration of the loop, write down the values.
You can watch this video or read through the content below it.
Problem: Given the following code, what is the output if the user enters the values: 10, 15, 20, 25, 30, 35, -1?
System.out.println("Enter a negative score to signal the end of input.");
int gdScores = 0;
int score;
System.out.print("Score: ");
Scanner get = new Scanner(System.in);
score = get.nextInt();
while (score >= 0)
{
if (score >= 20)
gdScores++;
System.out.print("Score: ");
score = get.nextInt();
}
System.out.println("Number of good scores: " + gdScores);
Subsection 5.7.1 SG1: Diagram which statements go together.

Subsection 5.7.2 SG2: Define and initialize variables
Start:
score = 10;
End:
score < 0

Subsection 5.7.3 SG3: Trace the loop

Number of good scores: 4
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