Java Basics

A variable is just a named box in memory that holds a value.

Java needs to know exactly what kind of data it's dealing with before it can store or process it.

Java has eight primitive data types — the most basic building blocks for storing data.

Non-primitive data types — also called reference types — are everything beyond Java's eight primitives.

A literal is a fixed value written directly in your source code — 42, 3.14, 'A', true, "Hello".

Type casting is converting a value from one type to another.

Widening casting is the automatic conversion of a smaller data type to a larger one.

Narrowing casting converts a larger data type into a smaller one.

Operators are the symbols that tell Java what to do with values — add them, compare them, combine them, assign them.

Arithmetic operators perform mathematical operations on numeric values.

Relational operators compare two values and always produce a boolean result — true or false.

Logical operators combine boolean expressions into more complex conditions.

Bitwise operators work directly on the binary representation of integers — manipulating individual bits.

Assignment operators store values into variables.

Unary operators take a single operand. Java has five: unary plus, unary minus, increment, decrement, and logical NOT. The increment and decrement operators have prefix…

The ternary operator is Java's only three-operand operator.

instanceof checks whether an object is an instance of a specific class or interface.

Input and output (I/O) in Java is how a program communicates with the outside world — reading data from the keyboard, files, or network, and writing data to the screen…

The Scanner class (java.util.Scanner) is the standard way to read user input from the keyboard in Java.

BufferedReader wraps a Reader (typically InputStreamReader wrapping System.in or a FileReader) and adds an internal buffer that dramatically reduces the number of…

The System.console() method returns a Console object that provides direct access to the character-based console (terminal) attached to the JVM.

printf() formats output using a format string containing literal text and format specifiers that are replaced with the values of subsequent arguments.

Escape sequences are special character combinations beginning with a backslash that represent characters which cannot be typed directly in a string or character literal…

Command line arguments are values passed to a Java program when it is launched from the terminal.