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Answers to Questions and Exercises: Operators

### Answers to Questions

> 1. Consider the following code snippet:

>    >     arrayOfInts[j] > arrayOfInts[j+1]

>    Question: What operators does the code contain?
>    Answer: `>`, `+`
> 2. Consider the following code snippet:

>    >     int i = 10;
>    >     int n = i++%5;

>    1. Question: What are the values of `i` and `n` after the code is executed?
>       Answer: `i` is 11, and `n` is 0.
>    2. Question: What are the final values of `i` and `n` if instead of using the postfix increment operator (`i++`), you use the prefix version (`++i)`)?
>       Answer: `i` is 11, and `n` is 1.

> 3. Question: To invert the value of a `boolean`, which operator would you use?
>    Answer: The logical complement operator "!".

> 4. Question: Which operator is used to compare two values, `=` or `==` ?
>    Answer: The `==` operator is used for comparison, and `=` is used for assignment.

> 5. Question: Explain the following code sample: `result = someCondition ? value1 : value2;`
>    Answer: This code should be read as: "If `someCondition` is `true`, assign the value of `value1` to `result`. Otherwise, assign the value of `value2` to `result`."

### Exercises

> 1. Change the following program to use compound assignments:

>    >     class ArithmeticDemo {

>    >          public static void main (String[] args){

>    >               int result = 1 + 2; // result is now 3
>    >               System.out.println(result);

>    >               result = result - 1; // result is now 2
>    >               System.out.println(result);

>    >               result = result * 2; // result is now 4
>    >               System.out.println(result);

>    >               result = result / 2; // result is now 2
>    >               System.out.println(result);

>    >               result = result + 8; // result is now 10
>    >               result = result % 7; // result is now 3
>    >               System.out.println(result);

>    >          }
>    >     }

>    Here is one solution:

>    >     class ArithmeticDemo {

>    >          public static void main (String[] args){
>    >               int result = 3;
>    >               System.out.println(result);

>    >               result -= 1; // result is now 2
>    >               System.out.println(result);

>    >               result *= 2; // result is now 4
>    >               System.out.println(result);

>    >               result /= 2; // result is now 2
>    >               System.out.println(result);

>    >               result += 8; // result is now 10
>    >               result %= 7; // result is now 3
>    >               System.out.println(result);

>    >          }
>    >     }

> 2. In the following program, explain why the value "6" is printed twice in a row:

>    >     class PrePostDemo {
>    >          public static void main(String[] args){
>    >               int i = 3;
>    >     	  i++;
>    >     	  System.out.println(i);	// "4"
>    >     	  ++i;
>    >     	  System.out.println(i);	// "5"
>    >     	  System.out.println(++i);	// "6"
>    >     	  System.out.println(i++);	// "6"
>    >     	  System.out.println(i);	// "7"
>    >          }
>    >     }

>    The code `System.out.println(++i);` evaluates to 6, because the prefix version of `++` evaluates to the incremented value. The next line, `System.out.println(i++);` evaluates to the current value (6), then increments by one. So "7" doesn't get printed until the next line.

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