Data types, variables and constants

Question 1

Data types

Answer 1

• Data that can be handled by a computer can
be of many types such as Character, Numeric,
String etc.
• Java classifies data types as follows:
– Primitive or in-built data type
– Reference data type

Question 2

Primitive Data Types

Answer 2

Primitive Data Types
• Primitive data types (also known as the
fundamental data types) are the inbuilt data
types offered by Java.
• Java provides 8 primitive data types which are
categorized as follows:
– Integral
• byte, short, int, long
– Fractional
• float, double
– Character
• char
– Boolean
• boolean

Question 3

Sizes of integral data types

Answer 3

byte: 1 byte
short: 2 bytes
int: 4 bytes
long: 8 bytes

Question 4

Ranges of integral data types

Answer 4

byte: -128 to +127
short: -32768 to +32767
int: -2 billion to +2 billion i.e -2^31 to 2^31 -1
long: -2^63 to +2^63 - 1

Question 5

Sizes of fractional data types

Answer 5

float: 4 bytes
double: 8 bytes

Question 6

Ranges of fractional data types

Answer 6

float: -3.4E+38 to +3.4E+38
double: -1.7E + 308 to 1.7E + 308

Question 7

Precision of fractional data types

Answer 7

float: 6 digit single precision
double: 15 digit double precision

Question 8

Size and range of char data type

Answer 8

size: 2 bytes
range: 0 to 65535

Question 9

Size or range of boolean data type

Answer 9

size: 8 bits, uses 1 bit
range: true or false

Question 10

Reference Types

Answer 10

Inbuilt reference types
– Arrays
– Strings
• User-defined reference types (also known as
user-defined objects or user-defined data
types)

Question 11

Variables

Answer 11

• A variable is a named storage location in the
computer’s memory.
• It can hold only one value of a particular data
type.
• The value in a variable can be manipulated
during the execution of the program.

Question 12

Constants

Answer 12

• A constant is a variable whose value cannot
be changed once it has been assigned a
value. If the value is changed subsequently in
the program, the compiler gives an error.
• The keyword final makes a variable as
constant.

Question 13

Advantages of Constants

Answer 13

• Indicates to the programmer that the value in
that constant (variable) cannot be changed and
hence makes it easier to read and check for
correctness. Even if the programmer accidentally
changes the value of that constant in the code,
the compiler gives an error.

• If the value in the constant needs to be changed,
only the declaration needs to be modified. On
the other hand if a literal is used, one has to
search through the entire program for every
occurrence of that specific value and then
change all the occurrences.

Question 14

Suffixes

Answer 14

• Suffixes are used to explicitly specify the data type of a literal data value.
• In some situations it is required, because the compiler
gives an error, when the value that is assigned to a
variable is beyond the capacity of the variable on the left hand side.