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Lesson: Language Basics
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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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