Branching ch.3

Question 1

myInt == 42

Answer 1

OK

Question 2

myChar == ‘q’

Answer 2

OK

Question 3

myDouble == 3.26

Answer 3

NOT OK

Question 4

myString == “Hello”

Answer 4

NOT OK

Question 5

=>

Answer 5

not valid operator

Question 6

!

Answer 6

not valid operator

Question 7

<>

Answer 7

not valid operator

Question 8

Can you use use = in an if-else expression?

Answer 8

No, should be ==

Question 9

How to detect a range?

Answer 9

Use if-else-if-else

Question 10

How do if-else-if-else structures work?

Answer 10

Each expression only needs to indicate the upper range part; if execution reaches an expression, the lower range part is implicit from the previous expressions being false.

Question 11

What is the range for 
if x < 10
else if x < 20
else if x < 30
else

Answer 11

0-9
10-19
20-29
30+

Question 12

In an if 
else if 
else if 
else 
structure is the second branch taken if the first if is not false?

Answer 12

the second branch expression is only reached if the first expression is false. So the second branch is taken if userAge < 16 is false (so 16 or greater) AND userAge is < 25, meaning userAge is between 16 - 24 (inclusive).

Question 13

Which approach uses a logical operator to detect if x is in the range 1 to 99.
0 < x < 100
(0 < x ) && (x < 100)
(0 < x) && (x > 100)

Answer 13

(0 < x) AND (x < 100)

Question 14

Write expression: x is in the range -4 to +4

Answer 14

(x > -5) && (x < 5)

Question 15

What happens when you omit the break statement in switch statements? Common error

Answer 15

Omitting the break statement for a case will cause the statements within the next case to be executed. Such “falling through” to the next case can be useful when multiple cases, such as cases 0, 1, and 2, should execute the same statements.

Question 16

str1 less than str2 returns what?

Answer 16

Negative number

Question 17

What is the expression for str1 less than str2?

Answer 17

str1.compareTo(str2) < 0

Question 18

str1 equal to str2 returns what?

Answer 18

0

Question 19

What is the expression for str1 equal to str2?

Answer 19

str1.compareTo(str2) == 0

Question 20

str1 greater than str2 returns what?

Answer 20

Positive number

Question 21

What is the expression for str1 greater than str2?

Answer 21

str1.compareTo(str2) > 0

Question 22

A programmer can compare strings while ignoring case using

Answer 22

str1.equalsIgnoreCase(str2) and str1.compareToIgnoreCase(str2).

Question 23

What value does the variable str have at the end of the program segment below?
String str = "Hello World!";
if (str.length() > 6) {
  str = "Changed!";
}
// What value does str have here?

Answer 23

“Changed!”

Question 24

Which of the following is a boolean expression that is true if the variable a has the value of 3?

Answer 24

3 == a

a == 3

Question 25

Which of the following is the reason to NOT use equality (==) to test double values against each other?

Answer 25

Double values in Java are approximate values, not exact, so rounding errors can occur.

Question 26

What value does the variable answer have after this code is executed?
boolean x = false, y = false;
boolean answer = x || !y;

Answer 26

true

Question 27

What value does the variable answer have after this code is executed?
boolean x = false, y = true, z = true;
boolean answer = y && ( x || !z );

Answer 27

false

Question 28

Which of the following is a correct way for checking if two String values stored in the variables str1 and str2 are equal?

Answer 28

str2.equals(str1)
str1.equals(str2)
NOT str2 == str1

Question 29

str1 = “normal”
str2 = “parallel”
if (str1.compareTo(str2) < 0)
str1 = str2;

Answer 29

str 1 = “normal”
str 2 = “parallel”

str 1 = “parallel”
str 2 = “parallel”

Question 30

Which of the following are reference types?
Scanner
int
char
String

Answer 30

Scanner

String

Question 31

Why can’t we use the equality operator (==) when comparing variables of reference types?

Answer 31

Location, location, location!
Because the variables hold the locations in memory of the objects, and the equality operator (==) tests if the two locations are the same not the values of the objects.

Question 32

What is the main difference between primitive types and reference types?

Answer 32

Variables of primitive types hold numbers that we use directly, variables of reference types hold numbers that are locations in memory where objects are stored.

Question 33

What gets printed to the screen when the following code segment executes?
int score = 1024;
String msg = "Default";
if (score > 300) {
    msg = "More than 300!";
}
else if (score > 500) {
    msg = "More than 500!";
}
else if (score > 1000) {
    msg = "More than 1000!";
}
System.out.println(msg);

Answer 33

More than 300!

Question 34

Scanner keyboard = new Scanner(System.in);
System.out.print("Enter a number: ");
int num = Integer.parseInt(keyboard.nextLine());
while ( CONDITION ) {
    System.out.println("That number is positive!");
    System.out.print("Enter another: ");
    num = Integer.parseInt(keyboard.nextLine());
}

Answer 34

num>=0
0<=num
0 <= num
num >= 0

Question 35

String str = "";
int idx = 0;
while (idx < 3) {
    if (idx % 2 == 0) {
        str = str + "a";
    }
    else {
        idx = idx + 1;
    }
}
System.out.println(str);

Answer 35

No output will happen because this loop has a bug in it.