Java Basics Vocabulary (Video Notes)

Vocabulary flashcards covering Java basics, data types, packaging, classes, methods, GUI tools, strings, casting, and wrapper classes.

Package

A collection of related classes; a sub-directory in your project; the package name must match its path in the src folder.

Class

A blueprint for objects that defines their data (fields) and behavior (methods).

Public class

A class declared public; only one public class allowed per source file, and its name must match the filename.

.class file

A compiled Java file containing bytecode; not human-readable.

Field

Variables inside a class that hold the object's data.

Method

Functions that operate on the data of an object.

Static field

A field that belongs to the class itself, not to any particular object instance.

Main method

The entry point of a Java program: public static void main(String[] args).

Primitive Data Types

Java’s built-in types, including int, double, boolean, char, byte, short, long, and float.

int

A 32-bit signed integer data type.

double

A 64-bit floating-point data type with double precision; one of the three emphasized on the AP exam (along with int and boolean).

boolean

A true/false data type.

char

Represents a single Unicode character.

float

A 32-bit floating-point data type; precision is half that of double.

byte

An 8-bit signed integer.

short

A 16-bit signed integer (2 bytes).

long

A 64-bit signed integer (8 bytes).

modulo ( %)

The modulo operation; returns the remainder after division.

Casting

Explicit conversion from one primitive type to another (e.g., (int) price).

Floor

Rounding down to the nearest integer; casting a positive double to int yields the floor value.

Integer.parseInt

Static method in Integer that converts a String to an int (example of a wrapper class utility).

Wrapper Classes

Classes that wrap primitive types as objects: Integer, Double, Character.

Integer

Wrapper class for the int primitive; includes methods like parseInt.

String

A class representing a sequence of characters; strings are objects, not primitive types.

String.equals

Compares two strings for exact, case-sensitive equality.

String.equalsIgnoreCase

Compares two strings for equality ignoring case differences.

String.length

Returns the number of characters in the string.

String.toUpperCase

Returns a new string with all characters converted to upper case.

String.toLowerCase

Returns a new string with all characters converted to lower case.

String.indexOf

Returns the index of the first occurrence of a character or substring, or -1 if not found.

String.substring

Returns a portion of the string between specified start and end indices.

IDE

Integrated Development Environment; software for writing, compiling, and debugging code.

JVM

Java Virtual Machine; runs Java bytecode.

Swing

Classic Java GUI toolkit; part of the javax.swing package.

JavaFX

Modern GUI toolkit designed as a replacement for Swing; not automatically included with the JDK since version 11.

package path rule

The package name must correspond to its directory path under the src folder.

Public

Access modifier indicating visibility; in Java, a file can have one public class whose name matches the filename.

static

Keyword for class-level members or methods (shared by all instances), as opposed to instance-level.

void

Return type indicating a method does not return a value.