Java

Create classes with fields, constructors and methods, and protect data with private.

Build class families with extends, override methods and treat different objects the same way.

Define contracts that many different classes can promise to follow.

Store growing lists and key–value data with Java’s powerful collection classes.

Catch problems with try/catch/finally, and throw your own exceptions for bad input.

Design a mini library system with classes, a LinkedHashMap and exceptions.