Generic Methods and Classes in Java

Introduction

• Topic: Discussion on generic methods and generic classes in Java.
• Purpose: To enable the use of types as parameters in Java classes, interfaces, and methods.

Benefits of Generics

• Eliminates the need for multiple versions of methods/classes for various data types.
• Allows one version of a method or a class for all reference data types.

Example with Arrays

• Different arrays: int[], double[], char[], and String[].
• Normally, multiple methods are needed to handle different data types.
• Using generics, one method can handle all reference data types.

Creating Generic Methods

1. Definition:
   • Use angle brackets before return type.
   • Common practice: Use T (or custom identifier like Thing).
2. Example:
   • Replace specific data type with the generic type T.
   • public static <T> void displayArray(T[] array).

Example: Generic Method with Return

1. Definition:
   • Use angle brackets before the method name.
   • Adjust return type to the generic type T.
2. Example:
   • public static <T> T getFirst(T[] array).
   • Returns the first element of the array.

Practical Scenario

• Example: Drawing various game sprites using a generic method instead of individual methods for each type.

Creating Generic Classes

1. Definition:
   • Use angle brackets after the class name.
   • Common practice: Use T or custom identifier.
2. Example:
   • Class definition: public class MyGenericClass<T>.
   • Variable type: T variable.
   • Constructor and methods using T.

Comparison with Standard Classes

• Standard classes are created for each data type (MyIntegerClass, MyDoubleClass, etc.).
• Generic class simplifies this by handling all data types.
• Example: MyGenericClass<Integer> handles integers, MyGenericClass<Double> handles doubles, etc.

Similarity with ArrayList

• Instantiation: ArrayList<String> myFriends = new ArrayList<>();.
• Comparison with generic class instantiation.
• ArrayList class also uses generics (ArrayList<E>).

Multiple Generic Parameters

• Scenario: Generic class with multiple parameters (<T, V>).
• Allows handling of multiple types in one class.
• Example: MyGenericClass<Integer, String>.

Bounded Types

1. Definition:
   • Limits the scope of data types a generic class/method can accept using extends.
2. Example:
   • public class MyGenericClass<T extends Number> limits T to subclasses of Number (like Integer, Double).

Summary

• Generics provide flexibility and efficiency in handling various data types in Java.
• Allows consolidation of methods and classes for all reference data types.
• Bounded types provide additional control over allowed data types.