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lab08a
booleans: and and or

Recall that && and || each take two booleans, and return a boolean. For example:

// These evaluate to either true or false, depending
// on what value the variables have:

(ptsPossible == 0) || (ptsEarned / ptsPossible > 0.85)

(numTickets <= seatsOnPlane) || (seatsOnPlane > 0)

Discussion question:

// SOME INCORRECT CODE:

String waterForm( double temp ) {
  if (temp < 32 && > 212) {
    return "not liquid";
    }
  else {
    return "liquid";
    }
  }

What syntax error does the above code have? (Is the compiler's error message helpful? Why or why not?) How should it be fixed?
What logic error does the above code contain? How should it be fixed?

Your task: P5.12 from the textbook: Revise BankAccount so that:

If a deposit is less than zero, ignore it. (That is, don't change the balance at all ¹.)
Similarly, if a withdrawal is less than zero or more than the balance, ignore it.
If a negative initial-balance is passed to the constructork, the balance is initialized to 0 instead.

Here is the BankAccountTester.java and BankAccount.java we wrote in class.

First add test cases which include:

Passing a negative amount to the constructor;
passing a negative amount to deposit;
passing a negative amount to withdraw;
passing a too-large amount to withdraw.

Of course, after each of these calls, you should verify that the balance is unchanged. Then modify the code. When verifying that a withdrawal amount is valid, use one of && or || (instead of using nested if-elses).

¹If you also want to print a warning message to System.err, that would be eminently reasonable, but not required. ↩

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©2009, Ian Barland, Radford University
Last modified 2009.Mar.17 (Tue) Please mail any suggestions
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lab08a booleans: and and or

lab08a
booleans: and and or