How do Generic Methods in Java Ensure Type Safety and Reusability?

Understanding Generic Methods in Java

In Java, it is possible to declare methods with generic types, which provides type-safe, reusable code for various data types. One such example is this method:

public <E extends Foo> List<E> getResult(String s);

where Foo represents a custom class.

Return Type vs. Generic Type

At first glance, it may appear that this method has multiple return types: List and E. However, this is not the case. The method in question has a single return type:

• List

Generic Type Declaration

The section is not a return type, but rather a generic type declaration. It specifies that:

• E is a generic type that:

  • Extends the Foo class
• The method can process any subtype of Foo by using this generic type.

Example Usage

Consider the following example:

class Bar extends Foo { }
...
List<Bar> result = getResult("some string");

In this case, the getResult method returns a List, since Bar is a subclass of Foo and satisfies the generic type requirement.

Conclusion

Generic methods provide flexibility and type safety by allowing you to define methods that work with specific classes or their subclasses. The generic type declaration in getResult allows it to handle subclasses of Foo and return lists of those types.

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