Java is a statically typed language, meaning all variables must be declared before they can be used. It has two categories of data types: Primitives and Reference Types.

These are predefined by the language and named by a keyword.

• int (4 bytes), long (8 bytes)
• float (4 bytes), double (8 bytes)
• char (2 bytes, Unicode)
• boolean (true/false)
• byte (1 byte), short (2 bytes)

Reference types are objects that wrap primitive types.

• Integer, Long, Double, Character, Boolean
• Autoboxing: Automatic conversion from primitive to wrapper (e.g., int to Integer).
• Unboxing: Automatic conversion from wrapper to primitive.

java Standard
int primitiveInt = 10;
Integer wrapperInt = primitiveInt; // Autoboxing

double price = 19.99;
Double wrappedPrice = price;

System.out.println("Max Integer: " + Integer.MAX_VALUE);

• Precision Loss: Using float for monetary values (use BigDecimal instead).
• NullPointerException: Forgetting that wrapper classes can be null, while primitives cannot.
• Reference Equality: Using == instead of .equals() when comparing wrapper objects like Integer.