Question

I have a project in my programming class and I’m failing a test case. I look into the test driver and find this:

 private static boolean testSquareArch()
  {
  boolean pass = true;
  int test = 1;
  int cnt;
  Square sq;
  Class cl;

  System.out.println("Square architecture tests...");

  sq = new Square(true, true, true, true, 0, 0);

  cl = sq.getClass();
  cnt = cl.getFields().length;
  pass &= test(cnt == 5, test++);  //FAILING THIS TEST

What does this do and how does it check my code?

Also while I’m here, what does this do?

  // Count and test number of of PACKAGE fields
  cnt = cl.getDeclaredFields().length
      - countModifiers(cl.getDeclaredFields(), Modifier.PRIVATE)
      - countModifiers(cl.getDeclaredFields(), Modifier.PROTECTED)
      - countModifiers(cl.getDeclaredFields(), Modifier.PUBLIC);
  pass &= test(cnt == 5, test++);  // Test 8 

I’m failing these test cases and just want to know why. Thanks

Answer 1

If you’re wondering about &=, here’s a quote from JLS 15.22.2. Boolean Logical Operators &, ^, and |.

For &, the result value is true if both operand values are true; otherwise, the result is false.

The operators & and | for booleans are the lesser known cousins of && (15.23) and || (15.24). The latter two are “conditional” operators; they short-circuit and only evaluate the right hand side if it’s actually needed.

The && operator is like & (§15.22.2), but evaluates its right-hand operand only if the value of its left-hand operand is true.

&= is the compound assignment version of &. See JLS 15.26.2. Compound Assignment Operators.

A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T is the type of E1, except that E1 is evaluated only once.

In other words, these are equivalent (assumed boolean b):

b &= bool_expr;
b = b & bool_expr;
if (!bool_expr) b = false;

---

This may also be your issue (java.lang.Class#getDeclaredFields):

Returns an array of Field objects reflecting all the fields declared by the class or interface represented by this Class object. This includes public, protected, default (package) access, and private fields, but excludes inherited fields.

Your count may not be correct if you want to also count the inherited fields.