Quick Answer

Implement type-safe collections and methods.

Understanding the Issue

Generics enable types (classes/interfaces) to be parameters. Provides compile-time type checking and eliminates casting. Use with collections, classes, methods.

The Problem

This code demonstrates the issue:

Java Error 
// Non-generic (unsafe)
List list = new ArrayList();
list.add("test");
Integer i = (Integer) list.get(0); // Runtime error

The Solution

Here's the corrected code:

Java Fixed 
// Generic solution
List<String> safeList = new ArrayList<>();
safeList.add("test");
String s = safeList.get(0); // Type safe

// Generic method
public <T> void printArray(T[] array) {
    for (T element : array) {
        System.out.println(element);
    }
}

Key Takeaways

Generics improve type safety and reduce casting.