Data Types & Arithmetic

Question 1

Primitive data types

Answer 1

Data types that cannot be used to create objects, but only variables that hold a single value. There are 8 primitive data types in Java and these variables do not have attributes or methods.

Question 2

What are the primitive data types in Java?

Answer 2

In ascending order of size:

1. Boolean (1 bit) - this type returns true or false
2. Byte - a number made up of 8 bits. Essentially all manufactured computers use a byte as the smallest unit of storage in memory.
3. Char (2 bytes) - characters that use the Unicode encoding scheme
4. Short (2 bytes) - integers, a number that cannot have a fractional part, in the range of -32,768 to +32,767
5. Int (4 bytes) - integers in the range of -2,147,483,658 to +2,147,483,657
6. Long (8 bytes) - integers in the range of -9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
7. Float (4 bytes) - a single precision data type. It can store a floating-point, or fractional, number with 7 digits of accuracy.
8. Double (8 bytes) - a double precision data type. It can store a floating-point, or fractional, number with 15 digits of accuracy.

Question 3

Why are data types important?

Answer 3

Variables must be classified according to the their data type, which determines the kind of information that may be stored in them. It’s important to select the correct data type for variables since this determines their memory, format, and storage.

Question 4

Unary operators

Answer 4

Operators that only require one operand. For example, ( - ) gives the negative value of a number in Java. It can be expressed as: - 5 - number (with a variable)

Question 5

Binary operators

Answer 5

Operators that work with two operands, such as:

• + Addition
• - Subtraction
• * Multiplication
• / Division
• % Modulus (returns the remainder of a division)

Question 6

Ternary operator

Answer 6

There is only one operator that works with three operands in Java, the conditional operator. It is a shorthand method of expressing an if-else statement in the following format: BooleanExpression ? Value1: Value2;

Question 7

Combined assignment operators / Compound operators

Answer 7

Shortcuts for common operations:

• *+=** where x+=5; is x = x + 5;
• *-=** where y -= 2; is y = y - 2;
• **=** where z *= 10; is z = z * 10;
• */=** where a /= b; is a = a / b;
• *%=** where c %= 3; is c = c % 3;

Question 8

Strongly typed language

Answer 8

Java is a strongly typed language which means that before a value is assigned to a variable, Java checks the data type of the variable and the value being assigned to it to determine whether they are compatible.

Java will perform some conversions between data types automatically, but only if they will not result in the loss of any data.

Question 9

Widening conversion

Answer 9

In assignment statements where lower-ranked data types are stored in variables of higher-ranked data types, Java automatically converts the lower-ranked value to the higher-ranked type, which is known as a widening conversion.

For example:
double x;

int y = 100;

x = y; // performs a widening conversion

Question 10

Narrowing conversion

Answer 10

The conversion of a value to a lower-ranked data type. For example, converting a double to an integer would be a narrowing conversion. Given that this would result in data loss, Java does not perform them automatically.

Question 11

Incrementer

Answer 11

An operator, ++, that increments a variable by adding 1.

For example:
counter++; // adds 1 to the variable

Question 12

Decrementer

Answer 12

An operator, –, that subtracts 1 from the variable.

For example:
counter–; // subtracts 1

Question 13

Boolean

Answer 13

A data type with two possible values: true or false.

Question 14

Cast operator

Answer 14

Lets you manually convert a value from one type to a different type, even if a narrowing conversion will take place. Cast operators are unary operators that appear as a data type name enclosed in a set of parentheses.

For example:
number = (int)72.567;
value = (double)bankAccount;

* Note that when a cast operator is applied to a variable, it does not change the contents of the variable. It only returns the converted value.

Question 15

Integer Division

Answer 15

Taking the quotient of two integers and discarding the remainder. For example, if the following two numbers are integers in Java, then 11/4 is 2, not 2.75. This is a very common mistake to watch out for!

Question 16

Modulus

Answer 16

The % operator that computes the remainder of integer division.

Question 17

Operator associativity

Answer 17

The rule that governs in which order operators of the same precedence are executed. For example, in Java the - operator is left-associative because a - b - c is interpreted as (a - b) - c, and = is right-associated because a = b = c is interpreted as a = (b = c).

Question 18

Operator precedence

Answer 18

The rule that governs which operator is evaluated first. For example, in Java the && operator has higher precendence than the || operator. Hence a || b && c is interpreted as a || (b && c).