Midterms

Data types, Variable, operators, and expression

Primitive Data Types

• built into the java language.

• these are data that are not objects and have no methods.

Integer Types

• Includes Byte, Short, int, and long.

• are signed, positive, and negative values since java does not support unsigned values.

High-order bit

• defines the sign of an integer value, and java manages it differently by adding a special “unsigned right shift“ operation

Byte

• smallest integer type that represent a small number

• -128 and 127

Short

• -32768 and 32787

Int

• default option usually for java because when you use int or short it gets promoted to ___

• -2,147,483,648 to 2,147,484

Long

• hold a higher number compared to a regular integer.

• A capital letter “L“ is placed right after the value

• ex. 20987L;

Floating Point Types

• are also called “real numbers“

• used when evaluating an expression that need fractional accuracy such as the computation of square root or a transcendental.

Flaot

• single precision floating point. 

• takes half the space of a double precision so it may be faster on some processors. 

• f is placed to the right of the value

Double

• Double processors 

• can be faster than single precision on a modern processors that have been optimized for high-speed mathematical calculation. 

Character Types

• can be divided into two a.) bye for a character (ASCII) and b.) a type in itself (Unicode)

ASCII

• American Standard Code for Information Interchange

• a code that assigns numbers to letters, digits, etc

Unicode character

• made to support characters that are not traditionally used in (US) English and do not work with compilers.

Char data type

• was created to support the unicode characters

Boolean 

• used for logical values and can hold true or false value.

Abstract Data types

• based on primitive data types but with more functionality.

• ex. string

Constant

• value cannot be changed 

• final keyword

Variable

• values can be changed in a program 

• defined by the combination of an identifier, a type, and a optional initialization depending on the task to be performed 

Variable Naming Convention 

• variable names are nouns must begin with a lowercase letter

• If a variable name contains two letter the first word must start with a lowercase and the following words must start with an Uppercase

• variable names must start with a letter, dollar sign, or an underscore.

• keywords cannot be used as variable name

Literals 

• values that may be assigned to primitive- or string-type variables and constant.

Boolean literals

• are true and false cannot use numbers

Integer literals

• numeric data that can be represented as octal, hexadecimal, and binary literals

Octal

• starts with a zero prefixed

• ex. int sex = 6;

Hexadecimal

• number prefixed with 0x

• ex. int x = 0xffff;

Binary literal

• number starts with 0B or 0b

Floating-point literals

• numbers that have a decimal fraction.

• suffix letter F or f is added to the number otherwise will be flagged as loss of precision.

Character literals 

• must be enclosed in single quotes ‘‘

String literals

• enclosed in ““

Operators

• used to compute and compare values and test multiple conditions.

Arithmetic Operators

• mathematical operators 

• Operand = value to be computed

• Addition, subtraction, Multiplication, Division, and modulus.

Assignment Operators

• assigns the specific value, variable, and/or functions to another variable.

• Assignment, add, subtract, multiple, division assignment

Unary Operators

• only requires one operand

• Increment +1

• Decrement -1

• Logical Complement - inverts the value of boolen

Prefix or Pre-increment 

• ex. x = 7, then the value will be 8 because ++x = 8

suffix or post-increment

• ex. x = 12, then the value of x- - will be 11.

Comparison

• All mathematical operation involving comparison between two values  

Shift Operators 

• work on bits of data

• involves moving the bit pattern to the left or right.

Bitwise Operators

• perform operations bit-by-bit.

AND

• results in a 1 if both bits are 1, but if any other combinations results in a 0

OR

• results in a 0 when both the bits are 0. Any other combination results in 1.

XOR

• Results to 0 if bits are same values, if not results in 1.

Logical Operators

• used to combine the results of boolean expressions.

• share similarities to bitwise but is limited to boolean expressions.

Logical AND

• if both operands are non-zero, expression returns true, otherwise it returns false.

Logical OR

• If one or both the operands are non-zero, the expression returns true; otherwise, it returns FALSE.

Conditional Operators

• used to control the flow of the program. 

• mainly used in loop statement

Order of Precedence of Operators

Expression

• combination of variables, constant, literals, and operators to produce a single value.

Arithmetic Expression

• expression that returns a numeric value based on the operators and operands used

Assignment Expression

• expression that involves assigning a value to a variable.

Relational Expression

• expression that compares values using relational operators

Logical Expression

• expression involving logical operators.

Conditional Expression

• expression involving the use of the ternary operator (?:) to assign a value based on a condition.