Ch 2 - Operators and Statements

Question 1

Name the three types of Java operators

Answer 1

unary
binary
ternary

Question 2

All arithmetic operators may be applied to any java primitives, except which types?

Answer 2

boolean and string

Question 3

Only which operators can be applied to String values?

Answer 3

+ and +=

Question 4

Name the two short circuit logical operators

Answer 4

|| and &&

Question 5

Name the logical operators and what they are used for

Answer 5

& - AND - only true if both operands are true
| - INCLUSIVE OR - only false if both operands are false
^ - EXCLUSIVE OR - only true if the operands are different

Question 6

What is the resulting data type of the equation x * y where:
int x = 1;
long y = 33;

Answer 6

since one of the values is long and the other is int, the int value is promoted to a long.

Question 7

What is the data type of x + y, where
double x = 39.21;
float y = 2.1;

Answer 7

This is a trick questions because y is not properly formatted. Floating point literals are assumed to be double, unless postfixed with an f, as in 2.1f.

Question 8

What is the data type of x / y, where
short x = 10;
short y = 3;

Answer 8

x and y will both be promoted to int before the operation, resulting in an output type of int.

Question 9

What is the data type of x * y / Z, where
short x = 14;
float y = 13;
double z = 30;

Answer 9

x will automatically be promoted to int solely because it is a short and is being used in an arithmetic binary operation. The promoted x value will then be automatically promoted to a float so that it can be divided with y. The result of x * y will then be automatically promoted to a double, so that it can be multiplied with z, resulting in a double value.

Question 10

Name the four numeric promotion rules:

Answer 10

1. if two values have different data types, java will automatically promote one of the values to the larger of the two data types.
2. If one of the values is integral and the other is floating-point, java will automatically promote the integral value to the floating-point value’s data type.
3. Smaller data types, namely byte, short, and char, are first promoted to int any time they’re used with a java binary arithmetic operator, even if neither of the operands is int.
4. After all promotion has occurred and the operands have the same data type, the resulting value will have the same data type as its promoted operands.

Question 11

Given the following code, provide the values for x and y:
int x = 3;
int y = ++x * 5 / x-- + --x;
System.out.println("x = " + x);
System.out.println("y = " + y);

Answer 11

x = 2
y = 7

Question 12

How do you fix the following lines of code:
int x = 1.0;
short y = 1921222;
int z = 9f;
long t = 192301398193810323;

Answer 12

int x = (int) 1.0;
short y = (short)1921222; // Stored as 20678
int z = (int)9f;
long t = 192301398193810323L;

Question 13

Given the following code, provide the values for x and y:
long x = 5;
long y = (x=3);
System.out.println(x);
System.out.println(y);

Answer 13

x = 3
y = 3

Question 14

What is the output of the following code:
boolean b = false;
if (b = true) {
	System.out.println("its true");
} else {
	System.out.println("its not true");
}

Answer 14

its true

Question 15

What is the output of the following code:
boolean b = true;
if (b = false) {
	System.out.println("its true");
} else {
	System.out.println("its not true");
}

Answer 15

its not true

Question 16

What is the output of the following code:
int x1 = 1;
if (x1) {
	System.out.println("its true");
} else {
	System.out.println("its not true");
}

Answer 16

Compiler error on this line:

if (x1) {

Question 17

What is the output of the following code:
int x1 = 1;
if (x1 = 5) {
	System.out.println("its true");
} else {
	System.out.println("its not true");
}

Answer 17

Compiler error on this line:

if (x1 = 5) {

Question 18

The short-circuit operators are && and ||. They are nearly identical to the & and | logical operators except…

Answer 18

the right hand side of the expression may never be evaluated if the final result can be determined by the left hand side of the expression.

Question 19

What is the output of the following code?
int x = 6;
boolean y = (x >= 6) || (++x <= 7);
System.out.println(x);

Answer 19

Because x >= 6 is true, the increment operator on the right-hand side of the expression is never evaluated, so the output is 6.

Question 20

true/false: the following code compiles:

boolean x = true == 3;

Answer 20

false

Question 21

true/false: the following code compiles:

boolean y = false != “Giraffe”;

Answer 21

false

Question 22

true/false: the following code compiles:

boolean z = 3 == “Kangaroo”;

Answer 22

false

Question 23

What does the following code output:
boolean y = false;
boolean x = (y = true);
System.out.println(x);

Answer 23

true

Question 24

What does the following code output:
File x = new File("myFile.txt");
File y = new File("myFile.txt");
File z = x;
System.out.println(x == y);
System.out.println(x == z);

Answer 24

false

true

Question 25

Describe a ternary operator

Answer 25

booleanExpression ? expression1 : expression2;

Question 26

What is the value of x? int y = 10; int x = (y > 5) ? (2 * y) : (3 * y);

Answer 26

20

Question 27

true/false, the following code compiles: | System.out.println((y > 5) ? 21 : "Zebra");

Answer 27

true

Question 28

true/false, the following code compiles: | int animal = (y < 91) ? 9 : "Horse";

Answer 28

false

Question 29

``` What does the following code output: int y = 1; int z = 1; final int x = y<10 ? y++ : z++; System.out.println(y + "," + z); ```

Answer 29

2,1

Question 30

What are the data types supported by switch statements?

Answer 30

- byte and Byte - short and Short - int and Integer - char and Character - String - enum values

Question 31

What two primitive types are not supported when used by the switch statement?

Answer 31

boolean and long (and their wrapper classes)

Question 32

``` What does the following code output? int dayOfWeek = 5; switch(dayOfWeek) { default: System.out.println("Weekday"); break; case 0: System.out.println("Sunday"); break; case 6: System.out.println("Saturday"); break; } ```

Answer 32

Weekday

Question 33

``` What does the following code output? int dayOfWeek = 5; switch(dayOfWeek) { case 0: System.out.println("Sunday"); default: System.out.println("Weekday"); case 6: System.out.println("Saturday"); break; } ```

Answer 33

Weekday | Saturday

Question 34

The case statement from a switch statement must have what attributes?

Answer 34

must be a literal, enum constant, or final constant variable.

Question 35

``` In the following switch/case statement, which lines do not compile? private int getSortOrder(String firstName, final String lastName) { String middleName = "Patricia"; final String suffix = "JR"; int id = 0; switch(firstName) { case "Test": return 52; case middleName: id = 5; break; case suffix: id = 0; break; case lastName: id = 8; break; case 5: id = 7; break; case 'J': id = 10; break; case java.time.DayOfWeek.SUNDAY: id = 15; break; } return id; } ```

Answer 35

``` private int getSortOrder(String firstName, final String lastName) { String middleName = "Patricia"; final String suffix = "JR"; int id = 0; switch(firstName) { case "Test": return 52; case middleName: // DOES NOT COMPILE. not a final variable id = 5; break; case suffix: id = 0; break; case lastName: // DOES NOT COMPILE. although it is final, it is not constant because it is passed into the method. id = 8; break; case 5: // DOES NOT COMPILE. Not a string id = 7; break; case 'J': // DOES NOT COMPILE. Not a string id = 10; break; case java.time.DayOfWeek.SUNDAY: // DOES NOT COMPILE. not a string. id = 15; break; } return id; } ```

Question 36

true/false, A while loop may terminate after its first evaulation of the boolean expression

Answer 36

true

Question 37

true/false, a do-while loop guarantees that the statement or block will be executed at least once

Answer 37

true

Question 38

What would the following code result in: for ( ; ; ) { System.out.println("Hello World"); }

Answer 38

``` continuous loop outputting: Hello World Hello World Hello World Hello World Hello World ... ```

Question 39

true/false, each of the components of the for loop are optional. Example: for (int i = 0; i<10; i++) { System.out.println(i); }

Answer 39

true

Question 40

What would the output of the following code be: int x = 0; for (long y = 0, z = 4; x < 5 && y < 10; x++, y++) { System.out.println(y + ""); }

Answer 40

0 1 2 3 4

Question 41

What would the output of the following code be: int x = 0; for (long y = 0, x = 4; x < 5 && y < 10; x++, y++) { System.out.println(x + ""); }

Answer 41

Compiler error in the for line: for (long y = 0, x = 4; x < 5 && y < 10; x++, y++) { You cannot redeclare variable in the initialization block.

Question 42

What would the output of the following code be: for (long y = 0, int x = 4; x < 5 && y < 10; x++, y++) { System.out.println(x + ", " + y); }

Answer 42

Compiler error: for (long y = 0, int x = 4; x < 5 && y < 10; x++, y++) { Can't have multiple data types in the initialization block.

Question 43

What would the output of the following code be: for (long y = 0, x = 4; x < 5 && y < 10; x++, y++) { System.out.println(y + ""); } System.out.println(x);

Answer 43

Compiler error: System.out.println(x); x is out of scope here.

Question 44

``` What would the output of the following code be: String[] names = new String[3]; for (int name : names) { System.out.print(name + " "); } ```

Answer 44

Compiler error: for (int name : names) { Data types don't match.

Question 45

Which operators can have optional labels?

Answer 45

if-then, switch, and loops

Question 46

What does a break statement do?

Answer 46

A break statement transfers the flow of control out to the enclosing statement.

Question 47

What does a continue statement do?

Answer 47

The continue statement transfers control to the boolean expression that determines if the loop should continue. In other words, it ends the current iteration of the loop.

Question 48

``` What does the following code output: public static void main(String[] args) { FIRST_CHAR_LOOP: for (int a = 1; a <= 4; a++) { for (char x = 'a'; x <= 'c'; x++) { if (a==2 || x == 'b') continue FIRST_CHAR_LOOP; System.out.print(" " + a + x); } } } ```

Answer 48

1a 3a 4a

Question 49

``` What does the following code output: public static void main(String[] args) { for (int a = 1; a <= 4; a++) { for (char x = 'a'; x <= 'c'; x++) { if (a==2 || x == 'b') continue; System.out.print(" " + a + x); } } } ```

Answer 49

1a 1c 3a 3c 4a 4c

Question 50

``` What does the following code output: public static void main(String[] args) { for (int a = 1; a <= 4; a++) { for (char x = 'a'; x <= 'c'; x++) { System.out.print(" " + a + x); } } } ```

Answer 50

1a 1b 1c 2a 2b 2c 3a 3b 3c 4a 4b 4c

Question 51

What does the following code output: public static void main(String[] args) { int count = 0; ROW_LOOP: for(int row = 1; row <= 3; row++) { for(int col=1; col<=2; col++) { if (row * col % 2 == 0) continue ROW_LOOP; count++; } } System.out.println(count++); }

Answer 51

2 Remember that a continue statement cannot be used with an if/then, unless the if/then is included in a loop.