COP 2800 (Java Programming I) Homework Assignment #2

Answer the following questions as briefly (but completely) as possible:

1. Can the following three conversions involving casting be allowed?  If so, find the converted result.

       boolean b = true;
       int i = (int) b;
   
       int i = 1;
       boolean b = (boolean) i;
   
       int i = 1;
       String s = (String) i;

2. What is the printout of the code in (a) and (b): if number is 30?  If number is 35?

   1.      if (number % 2 == 0)
                 System.out.println(number + " is even.");
                 System.out.println(number + " is odd.");

   2.      if (number % 2 == 0)
                 System.out.println(number + " is even.");
              else
                 System.out.println(number + " is odd.");

3. How do you generate a random integer i such that
   1. 0 ≤ i < 20?
   2. 10 ≤ i < 20?
   3. 10 ≤ i ≤ 50?
4. What is the value of the expression (assume ch is a char):  (ch >= 'A' && ch <= 'Z')
   1. if ch is 'A'?
   2. if ch is 'p'?
   3. if ch is 'E'?
   4. if ch is '5'?
5. Write a switch statement that assigns to a String variable dayName with Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday, if the int variable day is 0, 1, 2, 3, 4, 5, and 6, accordingly.
6. If a variable is declared in the for loop control, can it be used after the loop exits?
7. The for loop on the left is converted into the while loop on the right.  What is wrong?  Correct it.

   int sum = 0; for (int i = 1; i <= 4; i++) { if (i % 3 == 0) continue; sum += i; }

   int i = 1, sum = 0; while (i <= 4) { if (i % 3 == 0) continue; sum += i; i++; }

8. Do the following two loops result in the same value in sum?

   1.      int sum = 0;
           for ( int i = 0; i < 10; ++i ) {
               sum += i;
           }

   2.      int sum = 0;
           for ( int i = 0; i < 10; i++ ) {
               sum += i;
           }

9. 1. After the break statement is executed in the following loop, which statement is executed?  Show the output.

      for (int i = 1; i < 4; i++) {
         for (int j = 1; j < 4; j++) {
            if (i * j > 2)
               break;
            System.out.println(i * j);
         }
         System.out.println(i);
      }

   2. After the continue statement is executed in the following loop, which statement is executed?  Show the output.

      for (int i = 1; i < 4; i++) {
         for (int j = 1; j < 4; j++) {
            if (i * j > 2)
               continue;
            System.out.println(i * j);
         }
         System.out.println(i);
      }

10. What is wrong in the following statements?
    1. System.out.printf("%5d %d", 1, 2, 3);
    2. System.out.printf("%5d %f" , 1);
    3. System.out.printf("%5d %f" , 1, 2);
11. Show the output of the following statements:
    1. System.out.printf("amount is %f %e\n" , 32.32, 32.32);
    2. System.out.printf("amount is %5.4f %5.4e\n", 32.32, 32.32);
    3. System.out.printf("%6b\n", (1>2));
    4. System.out.printf("%6s\n", "Java");
    5. System.out.printf("%-6b%s\n", (1>2), "Java");
    6. System.out.printf("%6b%-s\n", (1>2), "Java");
    7. System.out.printf("%6b%-8s\n", (1>2), "Java");
12. Write a Java regular expression (“regex”), that matches en_US (standard Americian) formatted whole numbers.  Such numbers are composed of only digits and commas.  For example:

    Input	Result From Correct Regex
    ,0	False
    ,	False
    1,20	False
    1,234,	False
    0	True
    12	True
    123	True
    1,234	True
    0,000	True
    100,000	True

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