1.9. Multiple Choice ExercisesΒΆ

    1-9-1: What does the following code print?

    System.out.println(2 % 3);
    
  • 2
  • Whenever the first number is smaller than the second, the remainder is the first number. Remember that % is the remainder and 3 goes into 2 0 times with a remainder of 2.
  • 0
  • This is the number of times that 3 goes into 2 but the % operator gives you the remainder.
  • 3
  • Try it. Remember that % gives you the remainder after you divide the first number by the second one.
  • 1
  • This would be correct if it was 3 % 2 since 2 would go into 3 one time with a remainder of 1.

    1-9-2: What does the following code print?

    System.out.println(19 % 5);
    
  • 3
  • This is the number of times that 5 goes into 19, but % is the remainder.
  • 0
  • This would only be true if the first number was evenly divisible by the second number.
  • 4
  • 5 goes into 19 3 times (15) with a remainder of 4 (19-15=4)
  • 1
  • This would be correct if it was 19 % 2, but here we are dividing by 5.

    1-9-3: What does the following code print?

    System.out.println(1 / 3);
    
  • 0.3333333333333333
  • This would be correct if it was 1.0 / 3 or 1 / 3.0.
  • 0
  • When two integers are divided the results will also be integer and the fractional part is thrown away.
  • It will give a run-time error
  • You would get a run-time error if it was 1 / 0, because you can not divide by zero.
  • 0.3
  • Try it. Is this what you get?
  • It will give a compile-time error
  • Integer division is allowed in Java. It gives an integer result.

    1-9-4: What does the following code print?

    System.out.println(2 + 3 * 5 - 1);
    
  • 24
  • This would be true if it was System.out.println(((2 + 3) * 5) - 1), but without the parentheses the multiplication is done first.
  • 14
  • This would be true if it was System.out.println(2 + (3 * (5 - 1))), but without the parentheses the multiplication is done first and the addition and subtraction are handled from left to right.
  • This will give a compile time error.
  • This will compile and run. Try it in DrJava. Look up operator precedence in Java.
  • 16
  • The multiplication is done first (3 * 5 = 15) and then the addition (2 + 15 = 17) and finally the subtraction (17 - 1 = 16).

    1-9-5: Given the following code segment, what is the value of b when it finishes executing?

    double a = 9.6982;
    int b = 12;
    b = (int) a;
    
  • 9.6982
  • This would be true if it was b = a. What does the (int) do?
  • 12
  • This is the initial value of b, but then b is assigned to be the result of casting the value in a to an integer. Casting to an integer from a double will truncate (throw away) the digits after the decimal.
  • 10
  • Java does not round when converting from a double to an integer.
  • 9
  • When a double is converted into an integer in Java, it truncates (throws away) the digits after the decimal.

    1-9-6: What does the following code do when it is executed?

    System.out.println(5 / 0);
    
  • It will print 0
  • This would be true if it was System.out.println(0 / 5)
  • It will give a run-time error
  • You can't divide by 0 so this cause a run-time error.
  • It will give a compile-time error (won't compile)
  • You might think that this would be caught at compile time, but it isn't.
  • It will print 5
  • This would be true if it was System.out.println(5 / 1)

    1-9-7: What will the following code print?

    System.out.println(1.0 / 3);
    
  • 0
  • This would be true if it was (1 / 3).
  • .3
  • It will give you more than just one digit after the decimal sign.
  • 0.3333333333333333
  • The computer can not represent an infinite number of 3's after the decimal point so it only keeps 14 to 15 significant digits.
  • 0.3 with an infinite number of 3's following the decimal point
  • The computer can not represent an infinite number of 3's after the decimal point.

    1-9-8: What are the values of x, y, and z after the following code executes?

    int x = 3;
    int y = x;
    int z = x * y;
    x++;
    
  • x = 3, y = 3, z = 9
  • This would be true if the x++ wasn't there.
  • x = 4, y = 3, z = 9
  • Fist x is set to 3, then y is also set to 3, and next z is set to 3 * 3 = 9. Finally x is incremented to 4.
  • x = 0, y = 3, z = 0
  • You might think that y = x means that y takes x's value, but y is set to a copy of x's value.
  • x = 4, y = 4, z = 9
  • You might think that y = x means that if x is incremented that y will also be incremented, but y = x only sets y to a copy of x's value and doesn't keep them in sync.
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