Units 1, 2, and 3 AP CS A

Integer

A primitive data type that stores an integer number from -2,147,483,648 to 2,147,483,647

Double

A primitive data type that stores a decimal number with high precision

Class

defines a new data type. It is the formal implementation, or blueprint, of the attributes and behaviors of the objects of that class.

parseInt( )

A method in java that takes the numerical value out of a string and converts that to an integer

Object

a specific instance of a class with defined attributes. Objects are declared as variables of a class type.

Constructors

code that is used to create new objects and initialize the object's attributes.

New

keyword used to create objects with a call to one of the class's constructors.

Instance Variables

define the attributes for objects.

Methods

define the behaviors or functions for objects

Dot (.) operator

used to access an object's methods.

Parameters

The values or data passed to an object's method inside the parentheses in the method call to help the method do its job.

Return values

values returned by methods to the calling method.

immutable

String methods do not change the String object. Any method that seems to change a string actually creates a new string.

Wrapper Classes

classes that create objects from primitive types, for example the Integer class and Double class.

Boolean

A primitive data type that stores a true or false value

Casting a Variable

Changing the type of a variable using (type) name

Modulo

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

String

Used to declare a variable of type String which is a sequence of characters or text

length()

returns the number of characters in a String object.

substring(int from, int to)

returns the substring beginning at index from and ending at index (to -1). The single element substring at position index can be created by calling substring(index, index + 1).

substring(int from)

returns substring(from, length()).

indexOf(String str)

returns the index of the first occurrence of str; returns -1 if not found.

equals(String other)

returns true if this (the calling object) is equal to other; returns false otherwise.

compareTo(String other)

returns a value < 0 if this is less than other; returns zero if this is equal to other; returns a value > 0 if this is greater than other.

int abs(int)

Returns the absolute value of an int value (which means no negatives).

double abs(double)

Returns the absolute value of a double value.

double pow(double, double)

Returns the value of the first parameter raised to the power of the second parameter.

double sqrt(double)

Returns the positive square root of a double value.

double random()

Returns a double value greater than or equal to 0.0 and less than 1.0 (not including 1.0!).

(int)(Math.random()*range) + min

moves the random number into a range starting from a minimum number. The range is the (max number - min number + 1). For example, to get a number in the range of 5 to 10, use the range 10-5+1 = 6 and the min number 5: (int)(Math.random()*6) + 5).

conditional

Used to execute code only if a Boolean expression is true.

DeMorgan's Laws

Rules about how to distribute a negation on a complex conditional.

if (Boolean expression)

used to start a conditional statement. This is followed by a statement or a block of statements that will be executed if the Boolean expression is true.

else

used to execute a statement or block of statements if the Boolean expression on the if part was false.

else if (Boolean expression)

sed to have 3 or more possible outcomes such as if x is equal, x is greater than, or x is less than some value. It will only execute if the condition in the 'if' was false and the condition in the else if is true.