Unit 4: Fundamental Data Types

Question 1

Primitive Data Types

Answer 1

Variables of Primitive types store values.
Do not have methods.
Integers are whole numbers (+, -, 0).
Floating numbers are real numbers.

Question 2

Why can’t we just use floating point numbers?

Answer 2

Integers require less memory space.
Floating numbers have problems with rounding.
Integers are processed faster.

Question 3

Values of int, & double

Answer 3

int = 4 bytes
double = 8 bytes

Question 4

int is default integer type in Java

Answer 4

stores integer value in range -2,147,483,648 . . . 2,147,483,647.

Question 5

double is default floating-point type in Java

Answer 5

stores double-precision.

floating point value in approx. range +- 10^308, with 15 significant decimal digits.

Question 6

boolean

Answer 6

stores boolean value: true or false

Question 7

Multiple variables of same type can be declared in one statement

Answer 7

EX:
double gpa, price, milesPerGallon;
Bug lady, cricket, ant;

Question 8

Convenient to initialize several variables to same value in one statement

Answer 8

EX:
gpa = price = milesPerGallon = 0.0;
Stores to the left.
Read from RIGHT to LEFT.

Question 9

Aliases

Answer 9

2 or more object variables refer to same object.

Question 10

Operators

Answer 10

5 operators (arithmetic).
Combines 2 or more values or expressions.
\+ Addition
- Subtraction
* Multiplication
/ Division
% Modulo or Remainder

Question 11

Integer Division

Answer 11

Integer division by integer is ALWAYS integer.

Question 12

Remainder/Modulo

Answer 12

Amount leftover after integer division.

Question 13

What happens if we try to change the value of our Constants?

Answer 13

COMPILE ERROR!!!

Question 14

Can a double be assigned to an int?

Answer 14

No! The decimal portion and 4 of the 8 bytes would have to be discarded.
Java won’t “demote” on it’s own.

Question 15

Can an int be assigned to a double?

Answer 15

Yes! To store a 4-byte integer in an 8-byte floating point number, Java just adds a decimal point.

Question 16

Magic Number

Answer 16

A number that appears in your code without explanation.

Always use named (symbolic) constants instead of “magic number” in code.

Question 17

Constants

Answer 17

Variable that can only be assigned a value once.
Compile Error if attempted to change value after initialized.
Often called “final variable”.

Question 18

Scanner Class

Answer 18

package: java.util - imported required.
Supports reading data from keyboard (standard input) and files.
Reads tokens - groups of characters separated by white spaces - or lines.
Converts input to numeric data types automatically.

Question 19

nextLine()

Answer 19

Method reads until encounters (new line).

Returns string before and then throws away the new line character.

Question 20

scan.nextInt()

Answer 20

Reads an integer, returns as an int

Question 21

scan.nextDouble()

Answer 21

Reads in floating-point number, returns as a double

Question 22

scan.next()

Answer 22

Reads next token, returns a string