Java 2 Operators And Assignments

Front 1

Can Java operators be overloaded?

Back 1

No

Front 2

Which operator comes overloaded out of the box?

Back 2

The + operator which if applied to a String concatenates the right-hand operand to the operand on the left.

Front 3

What are variables?

Back 3

just bit holders, with a designated type

Front 4

What does an object reference variable contain?

Back 4

bits representing a way to get to the object - it is a value representing a specific object on the heap or null.

Front 5

If the object reference value has not been assigned a value what does it hold?

Back 5

bits representing "null"

Front 6

What is the "assignment operator" and what does it do?

Back 6

the equal (=) sign and is used to assign a value to a variable

Front 7

What type is a literal integer(such as 7) always?

Back 7

an "int"

Front 8

What happens when you assign a literal integer to a byte variable?

Back 8

the compiler automatically narrows the literal value to a byte, i.e. the compiler puts in the cast

Front 9

What is the result of an expression involving anything "int"-sized or smaller?
What happens with this:
byte b = 3;
byte c = 8;
byte d = b + c;

Back 9

It is always an "int".

It won't compile - you get the error "possible loss of precision". If you put in the cast it will work:
byte d = (byte)(b + c);

Front 10

Every floating point literal is a _____ not ____.

Back 10

double
float

Front 11

What happens if you do:

float f = 32.3;

Back 11

It won't compile.

Front 12

What must you do to assign a floating-point literal to a "float" variable?

Back 12

You must either cast the value or append an "f" (or "F") to the end of the literal.

Front 13

What happens if you do:

byte a = 128;

Back 13

it won't compile - the compiler knows that it is too big to fit into the variable
"possible loss of precision"

Front 14

What happens when you do:

byte a = (byte)128

Back 14

You lose all the bits to the left of the bits you're narrowing to. So we are left with 10000000 where 1 is the sign bit so this is really -128.

Front 15

What actually happens when you do:
byte b = 3;
b += 7;

Back 15

it is equivalent to:

byte b = 3;
b = (byte)(b + 7);

so it lets you add to the value of b without putting in an explicit cast.

Front 16

When you assign one primitive variable to another, what happens?

Back 16

the contents of the right-hand variable are copied - they do not share a single value.

Front 17

What 3 things does the following line do:
Button b = new Button();

Back 17

1. Makes a reference variable named b, of type Button
2. Creates a new Button object on the heap
3. Assigns the newly created Button object to the reference variable b

Front 18

What does it mean to assign "null" to an object reference variable?

Back 18

it means the variable is not referring to any object

Front 19

You can use a reference variable to refer to any object that is a _____ of the declared reference variable type.

Back 19

subclass

Front 20

Can you change the value of a String object?

Back 20

No, they are immutable

Front 21

What happens when you use a String reference variable to modify a string?

Back 21

1. A new string is created, leaving the original String object untouched.
2. The reference used to modify the String is then assigned the brand new String object

Front 22

For any object type except String, what happens when two references refer to the same object and either of these references is used to modify the object?

Back 22

both references will see the change because there is still only a single object

Front 23

How many String objects are created in the following:

String s = "Fred";
String t = s;
t.toUpperCase();

Back 23

two String objects were created but the newly created String holding "FRED" is toast since it isn't assigned to a String variable; both t and s referr to the String "Fred".

Front 24

Comparison operators always result in a ______ value.

Back 24

boolean (true or false)

Front 25

What are the 4 comparison operators?

Back 25

> (greater than)
>= (greater than or equal to)
< (less than)
<= (less than or equal to)

Front 26

Can characters be used in comparison operators?

Back 26

Yes, when comparing a character with a character, or a character with a number, Java will take the ASCII or Unicode value of the character as the numerical value, and compare the numbers

Front 27

Can the "instanceof" operator be used for primitive variables?

Back 27

No, only for object reference variables

Front 28

What do you use the "instanceof" operator for?

Back 28

to check whether an object is of a particular class or interface type. It checks if the object referred to by the variable on the left side of the operator passes the IS-A test for the class or interface type on the right

Front 29

Any object reference will evaluate to true if you use the "instanceof" operator against type _____.

Back 29

Object

Front 30

An object is said to be of a particular type (meaning it will pass the "instanceOf" test) if any of the object's _______ implement the interface.

Back 30

superclasses

Front 31

What happens when you test whether a "null" object (or "null" itself) is an instance of a class?

Back 31

will always result in false

Front 32

Is an array an object or a primitive?

Back 32

It is an object, even if the array is an array of primitives

Front 33

An array is always an instanceof _____.

Back 33

Object

Front 34

What 2 operators test for equality?

Back 34

== equals
!= not equals

Front 35

The equality operators compare two things and return a ______ value.

Back 35

boolean

Front 36

Can you compare incompatible types?

Back 36

No

Front 37

What four different type of things can be tested for equality?

Back 37

1. Numbers
2. Characters
3. Boolean primitives
4. Object reference variables

Front 38

What happens if a floating-point number is compared with an integer and the values are the same as in (5.0 == 5L)?

Back 38

the == operator returns true

Front 39

Can integer values be used where a boolean value is expected?

Back 39

No

Front 40

What does the == operator test for when used with object reference variables?

Back 40

to see if they refer to the same object

Front 41

What are the 4 basic arithmetic operators?

Back 41

+ addition
- subtraction
x multiplication (use *)
/ division

Front 42

What does the % operator do?

Back 42

it is the remainder operator and divides the left operand by the right operand and the result is the remainder

Front 43

What happens when you divide an integer by zero?

Back 43

an ArithmeticException

Front 44

What happens when you use the % operator with a right operand of zero?

Back 44

an ArithmeticException

Front 45

What happens when you divide a floating-point number by positive zero?

Back 45

You get positive infinity

Front 46

What happens when you divide a floating-point number by negative zero?

Back 46

You get negative infinity

Front 47

Will you get an ArithmeticException when you use the remainder operator on floating-point numbers, where the right operand is zero?

Back 47

No

Front 48

When does the + operator become a String concatenation?

Back 48

When either operand is a String. If both operands are numbers, the + operator is the addition operator.

Front 49

What are the two operators that will increment or decrement a variable by one?

Back 49

++ increment (prefix and postfix)
-- decrement (prefix and postfix)

Front 50

What happens when you use the increment or decrement operator on a "final" variable?

Back 50

a compiler error, final variables can't be changed

Front 51

Give the 3 shift operators.

Back 51

>> right shift
<< left shift
>>> unsigned right shift(zero-filled right shift)

Front 52

Can you use shift operators on floating-point numbers?

Back 52

No

Front 53

How do you determine the result of a shift operator?

Back 53

you have to convert to binary

Front 54

With the left shift operator, what happens to the right side?

Back 54

the right side is filled with zeros

Front 55

When using the right shift operator, what happens to the left side?

Back 55

the leftmost bits are filled in on the left with whatever the sign bit was

Front 56

With the right shift operator, what happens to a negative number?

Back 56

It stays negative

Front 57

Except for a few special cases, the result of an unsigned right shift is always _____?

Back 57

positive, regardless of the original sign bit

Front 58

All operands in a bit shift are promoted to at least ____

Back 58

an int

Front 59

How many bits are shifted with the shift operators? How many bits are shifted when you shift an int by 34?

Back 59

always the right operand modulus the total number of bits for that primitive type.
2 bits

Front 60

If you shift an "int" by any multiple of 32 or a "long" by any multiple of 64, what do you get?

Back 60

the original value will not change

Front 61

What actually happens when you use the right shift operator?

Back 61

the number being shifted is "divided" by 2 to the power of the number of bits to shift.

Front 62

What actually happens when you use the left shift operator?

Back 62

the number being shifted is "multiplied" by 2 to the power of the number of bits to shift

Front 63

What are the 3 bitwise operators?

Back 63

& AND
| inclusive OR
^ exclusive OR

Front 64

What does the "&"operator do?

Back 64

compares corresponding bits between two numbers. If both bits are 1, the final bit is 1. If only one of the bits is 1, the resulting bit is 0.

Front 65

What does the "|" operator do?

Back 65

sets the resulting bit to 1 if either (of both) of the bits is a 1

Front 66

What does the "^" operator do?

Back 66

compares two bits to see if they are different. If they are different, the result is 1.

Front 67

What does the "~" operator do?

Back 67

it is the flip-the-bits operator. It will change all 1s to 0s and vice versa.

Front 68

Give the structure of the conditional operator.

Back 68

someVariable = (boolean expression) ? value to assign if true: value to assign if false

Front 69

Can you nest conditional operators into one statement?

Back 69

Yes

Front 70

What does "casting" let you do?

Back 70

Convert primitive values from one type to another.

Front 71

Typically, an implicit cast happens when you're doing a ______ conversion.

Back 71

widening

Front 72

The large-value-into-small-container conversion is referred to as _____.

Back 72

narrowing

Front 73

Which type of converions requires an explicit cast, widening or narrowing?

Back 73

narrowing

Front 74

What happens when you assign a floating-point number to an integer variable?

Back 74

a compiler error

Front 75

What are the 4 logical operators?

Back 75

&& short-ciruit AND
|| short-circuit OR
&
|

Front 76

The "&&" operator is similar to the "&" operator except for what?

Back 76

it evaluates only boolean values and can't be used as a bitwise operator.

Front 77

What does the "&&" operator do if the left side of the operation resolves to false?

Back 77

It doesn't bother looking at the right side of the operation

Front 78

What does the "||" operator do if the left side of the operation resolves to true?

Back 78

It doesn't bother looking at the right side of the operation.

Front 79

Can the bitwise operators (& and |) be used in both logical and bitwise expressions?

Back 79

Yes, but they are rarely used in logical expressions since they are not efficient - they evaluate both sides of the expression

Front 80

What happens when you pass an object reference variable into a method?

Back 80

both the caller and the called method will now have identical copies of the reference, and thus both will refer to the same exact (not a copy) object in the heap.

Front 81

Is Java "pass-by-reference" or "pass-by-value"?

Back 81

pass-by-value, which means pass-by-copy-of-the-variable so the called method can't change the caller's variable.

Front 82

What does shadowing involve?

Back 82

It involves declaring a variable that's already been declared somewhere else. The effect is to hide the previously declared variable in such a way that it may look as though you're using the shadowing variable

Front 83

When a floating-point zero is divided by zero, what do you get?

Back 83

NaN