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Answers to Questions and Exercises: Variables

Answers to Questions

1. Question: Identify all of the variables in the Sort program.
   Answer: Here's the sort program again with the variable declarations shown in red:

   public class Sort {
       public static void main(String[] args) {
           int[] arrayOfInts = { 32, 87, 3, 589, 12, 1076,
                                 2000, 8, 622, 127 };
   
           for (int i = arrayOfInts.length; --i >= 0; ) {
               for (int j = 0; j < i; j++) {
                   if (arrayOfInts[j] > arrayOfInts[j+1]) {
                       int temp = arrayOfInts[j];
                       arrayOfInts[j] = arrayOfInts[j+1];
                       arrayOfInts[j+1] = temp;
                   }
               }
           }
   
           for (int i = 0; i < arrayOfInts.length; i++) {
               System.out.print(arrayOfInts[i] + " ");
           }
           System.out.println();
       }
   }
   

2. Question: What is the name of each variable?
   Answer: args, arrayOfInts, i, j, temp, and i a second time. This program can use i twice because the two variables have different scope.

3. Question: What is the data type for each variable?
   Answer: args is an array of String objects. arrayOfInts is an array of integers. All of the other variables are integers.

4. Question: What is the scope for each variable?
   Answer: The following diagram shows the scope of each variable declared within the Sort program.
   

Answers to Exercises

1. Exercise: Rewrite the MaxVariables program to display the minimum value of each integer data type.
   
2. Exercise: Use a different method to discover if aChar is an upper case letter.
   
3. Exercise: Give aBoolean a different value.
   

Answers: Here's our solution to all three exercises, called MinVariables, with the differences shown in red:

public class MinVariables {
    public static void main(String args[]) {

        // integers
        byte smallestByte = Byte.MIN_VALUE;
        short smallestShort = Short.MIN_VALUE;
        int smallestInteger = Integer.MIN_VALUE;
        long smallestLong = Long.MIN_VALUE;

        // real numbers
        float smallestFloat = Float.MIN_VALUE;
        double smallestDouble = Double.MIN_VALUE;

        // other primitive types
        char aChar = 'S';
        boolean aBoolean = false;

        // display them all
        System.out.println("The smallest byte value is " + smallestByte);
        System.out.println("The smallest short value is " + smallestShort);
        System.out.println("The smallest integer value is " + smallestInteger);
        System.out.println("The smallest long value is " + smallestLong);

        System.out.println("The smallest float value is " + smallestFloat);
        System.out.println("The smallest double value is " + smallestDouble);

        if (Character.isLowerCase(aChar)) {
            System.out.println("The character " + aChar + " is lower case.");
        } else {
            System.out.println("The character " + aChar + " is upper case.");
        }
        System.out.println("The value of aBoolean is " + aBoolean);
    }
}

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