Abstract

The **Scanner** class in Java is used for reading input from various sources, like the console or files. It provides methods like `next()`, `nextInt()`, and `nextLine()` to read different data types. **Tokens** are the smallest elements in a program, like keywords, operators, and identifiers. Java uses tokens to build expressions and statements. **Constants** are values that do not change during program execution. They are defined using the `final` keyword, ensuring their value remains fixed. **Variables** are placeholders used to store data that can change during program execution. Java requires specifying a variable’s data type, like `int`, `String`, etc., to ensure correct usage and operations on the stored data.