Java in 21 Days (8th Edition) Day 7: Exceptions and Threads

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Notes and Corrections

View the Certification Practice quiz solution
Certification answer: Answer (c) is correct. The i variable should not be used when calculating the average because it goes up by 1 even when a command-line argument is not a valid floating-point number. For example, if you ran the application like this:
java AverageTest 1 1 1 x
The output would be the following:
Invalid input: x
Average value: 0.75
To correct the problem, the statement should be this:
System.out.println("Average: " + (sum / count));
Answer (a) is incorrect because the statement works correctly. In the conditional part of a for loop, you can put two expressions together with an & operator or one of the other logical operators.
Answer (b) is incorrect because the statement works correctly. Each element in the temps[] array is initialized to 0, so if a NumberFormatException is thrown in the for loop, sum += temps[i] will add 0 to the sum.
Answer (d) is incorrect because there was an error in the application.

Source Files

Activities

Solution 1: PrimeFinder2.java.
Solution 2: PrimeThreads2.java.