Alan Couze

In chapter 2 on page 57 there is an example on the pre/post increment and decrement operators:

int x = 3; int y = ++x * 5 / x-- + --x; System.out.println(" x is " + x); System.out.println(" y is " + y);

It explains that first, the x is incremented and returned:
int y = 4 * 5 / x-- + --x; // x assigned value of 4

However, on page 51, Table 2.1 it says that post-unary operators have higher precedence over pre-unary operators. So in this example why wouldn't the x be decremented to 2 first and return 3?

int y = ++x * 5 / 3 + --x; // x assigned value of 2, but 3 is returned

Then x would be incremented to 3

int y = 3 * 5 / 3 + --x; // x assigned value of 3

...and then x would be decremented back to 2:

int y = 3 * 5 / 3 + 2; // x assigned value of 2

int y = 15 / 3 + 2;
int y = 5 + 2;
int y = 7;

This yields the same result that the book states, but just in a different manner. Which is correct?

In Chapter 1 it explains that the following import statement is not valid when you want to import java.nio.file.Files and java.nio.file.Paths:

import java.nio.*;

However, I tried creating a couple of test packages and an import such as this seemed to work. For example, I created a Java class

import test1.*; public MyTest { public static void main(String[] args) { Test2 test2 = new Test2(); } }

And this code is located in directory test1/test2:

public class Test2 {}

The example above does error out by saying "MyTest.java:1: error: package test1 does not exist". However, if I add any Class to the test1 directory (i.e. "Test1") then the above compiles without error. So, it seems to me that the wildcard for imports will work correctly with sub-packages (i.e. test1.test2) but only if there are Classes in the parent package(s) (test1).

Is this a correct assumption?

I see what I did wrong. I missed the fact that the getTailLength(int) is an overloaded method - I missed the int parameter! Although at least the typos will be reported. Thanks.

There is a typo in the explanation of the Assessment test answer #4:

y = (1 + 2 * 2) % 3 = (1 + 4) % 3 = 4 % 3 = 2

This should be

y = (1 + 2 * 2) % 3 = (1 + 4) % 3 = 5 % 3 = 2

I'm either highly confused, or the answer key for Assessment question 3 is incorrect. It says that the answers are C, D, E.

I understand that 'C' is a correct answer, since there is an invalid override (more restrictive access modifier in the class is defined).

Answer 'D' does not seem to be a correct answer. The explanation says "Next, the class Cougar implements an overloaded version of getTailLength(), but since the declaration in the parent class Puma is invalid, it needs to implement a public version of the method. Since it does not, the declaration of Puma is invalid, so option D is correct." However, class Cougar does implement a public version of getTailLength().

'E' seems to be a correct answer, however the answer section says "Option E is incorrect, since Puma is marked abstract and cannot be instantiated." Shouldn't it say "Option E is correct"?

So I believe that C,E are correct answers, but D is not.