This lecture discusses Java variables, data types, and input/output. It covers the four main aspects of variables: name, type, size, and value. The lecture distinguishes between primitive types like int and double, which are basic Java types, and reference types like classes, which must be defined. It also introduces escape sequences for special characters and format specifiers for printing variables of different types.

1. Object Oriented
Programming
Lecture 2
Asif Shahzad
Assistant Professor
COMSATS University, Lahore Campus

2. Java Language Basics - Variables
• 4 things about a variables
• Name … Naming rules and conventions
• Type
• Size .. Bytes it consume in main memory
• Value .. Default value and literals
• Variable types in Java
• Primitive Types
• Reference Types

3. Primitive and Reference Types
• Primitive Types
• Basic variable types provided by Java languages
• Primitive types, literals, and ranges (of integral types)
• Reference Types
• These are usually created using primitives and other reference types
• There exist built-in reference types (Scanner, System, etc.) and we can
create our own reference types too
• Reference types are created by creating classes in Java … more details later

5. Java Language Basics – Escape Sequence
• Escape Sequences:
• b (backspace)
• t (tab)
• n (line feed)
• r (carriage return)
• " (double quote)
• ' (single quote)
• (backslash)

6. Java Language Basics
• Format Specifiers
• System.print* methods
• Getting different types of input from User