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Trail: Learning the Java Language
Lesson: The Nuts and Bolts of the Java Language

Answers to Questions and Exercises: Control Flow

Answers to Questions

  1. Two questions about WhileDemo(in a .java source file) and DoWhileDemo(in a .java source file).

    Question: What would the output be from WhileDemo(in a .java source file) and DoWhileDemo(in a .java source file) if you change the value of the string copyFromMe to "golly gee. this is fun"?
    Answer: WhileDemo displays nothing. DoWhileDemo displays golly.

    Question: Would the output be different? Defend your answer.
    Answer: The output is different. The expression c != 'g' is evaluated at the top of the loop in WhileDemo. Because the first character of the string is a 'g' the statements within the loop are never executed. In DoWhileDemo the expression is evaluated at the bottom of the loop after the first 'g' is appended to the string buffer. Thus the expression tests the second character in the string, which is an 'o'. The loop continues until the second 'g' in the string.

  2. Question: Identify the control flow statements in the Sort(in a .java source file) program.
    Answer:
    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();
        }
    }
    

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