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// Integer types
byte smallNum = 127;              // -128 to 127
short mediumNum = 32000;          // -32,768 to 32,767
int normalNum = 2_000_000;        // underscores for readability (Java 7+)
long bigNum = 9_876_543_210L;     // suffix L for long literals

// Floating point
float price = 19.99f;             // suffix f required
double precise = 3.141592653589;  // default decimal type

// Character and boolean
char letter = 'A';               // single character in single quotes
char unicode = '\u0041';          // Unicode A
boolean isActive = true;          // only true or false

// Number bases
int hex = 0xFF;      // hexadecimal (255)
int binary = 0b1010; // binary (10)
int octal = 0755;    // octal (493)

// String — most common reference type
String greeting = "Hello, World!";
String empty = "";
String nullStr = null;  // reference types can be null

// Arrays
int[] numbers = {1, 2, 3, 4, 5};
String[] names = new String[3];

// Objects
Object obj = new Object();
List<String> list = new ArrayList<>();

// Key difference: primitives store VALUES, references store ADDRESSES
int a = 5;
int b = a;        // b gets a COPY of the value
b = 10;           // a is still 5

String s1 = "Hello";
String s2 = s1;   // s2 points to the SAME object
// But Strings are immutable, so this is safe

// Wrapper classes: object versions of primitives
Integer boxedInt = 42;          // autoboxing: int -> Integer
int unboxed = boxedInt;         // auto-unboxing: Integer -> int

// Useful for collections (cannot store primitives directly)
List<Integer> numbers = new ArrayList<>();
numbers.add(10);    // autoboxed to Integer
int first = numbers.get(0);  // auto-unboxed to int

// Utility methods on wrapper classes
int parsed = Integer.parseInt("42");
String str = Integer.toString(42);
int max = Integer.MAX_VALUE;  // 2,147,483,647
double infinity = Double.POSITIVE_INFINITY;

// Null danger with unboxing
Integer maybeNull = null;
// int crash = maybeNull;  // NullPointerException!