CS Awesome - Unit 1 Vocabulary

Variable

A name associated with a memory location in the computer.

object variable

Holds a reference which points to the object in memory.

boolean

used to declare a variable that can only have the value true or false.

double

used to declare a variable that is a decimal number like 3.25.

int

used to declare a variable of type integer (a whole number like -3 or 235).

static

means that the field or method exists in the object that defines the class.

compiler

Software that translates the Java source code into the Java class file that can be run.

compiler/syntax error

An error or bug that is found by the compiler like a missing semicolon

logic error

error that has correct syntax but undesired output by the programmer

Class

• used to define a type of objects (classify something)

• creates Objects that do the actual work in object-oriented programming.

• Defines attributes of the object

• Allows for actions to be taken

attribute

data/properties of a class

method

type (class) with abilities/behaviors

Main Method

• Where execution starts in a Java program.

• used to test the class

constructor

• ways to initialize fields that have the same names as a class

• many constructors can be used for the same object

Boolean

An expression that is either true or false.

Camel Case

One way to create a variable name by appending several words together and uppercasing the first letter of each word after the first word (myScore).

Casting

• Changing the type of a variable using (type) name.

• i.e. rounding

  • Positive numbers: (int)(x + .5)

  • Negative number: (int)(x - .5)

System.out.println()

Java method that lets us print out a line of output followed by a newline to the user

Declare a Variable

Specifying the type and name for a variable. This sets aside memory for a variable of that type and associates the name with that memory location.

Initializing a Variable

The first time you set the value of a variable.

String literal

Text enclosed by double quotes.

modulo

The % operator which returns the remainder from one number divide by another.

Operator

Common mathematical symbols such as + for addition and * for multiplication.

Shortcut or compound assignment operators

Operators like x++ or x+= 1 which mean x = x + 1

assignment statements

• initialize or change the value stored in a variable using the assignment operator =.

• always has a single variable on the lefthand side

data type

determines the size of memory reserved for a variable, for example int, double, boolean, String.

ArithmeticException

If you divide by zero, you will get this error.

operator precedence

Some operators are done before others, for example *, /, % have precedence over + and -, unless parentheses are used.

arithmetic expression

a sequence of operands and operators that describe a calculation to be performed, for example 3*(2 + x)

increment operator

The operator (++) that increases the value of a numerical variable by one.

string literal

characters inside the quotation marks: “”

delimiter

• open and close curly braces that indicate to java to start and close a line

• {} are used to surround blocks of code such as methods or the contents of classes

• () are used in mathematical expressions and to surround parameter lists for method calls

• [] they are used for arrays (lists)

integer division

• arithmetic operation that uses two int values to evaluate to an int value (no decimal)

• i.e. ¾ = 0

System.out.println( String.format("%.02f", number) );

Decimal output formatted to only show 2 decimal places

postfix operator

• operator after the variable name

• value of the variable is changed after evaluating the variable to get its value.

prefix operator

• operator before the variable name

• value of the variable in incremented before the variable is evaluated to get the value of the expression