Introduction to Java Generics: Why Use Generics? Simple Understanding and Usage

Java Generics, a parameterized type feature introduced in Java 5, primarily addresses type-unsafe issues (such as ClassCastException at runtime caused by collections storing arbitrary types) and the cumbersome nature of forced type conversions when no generics are used. It enables type safety and code reuse. Application scenarios include generic classes (e.g., Box<T>), interfaces (e.g., Generator<T>), methods (e.g., <T> T getFirstElement(T[])), and standard collections (e.g., ArrayList<String>, HashMap<String, Integer>). Wildcards `<?>` enhance flexibility, with upper-bounded wildcards `<? extends T>` restricting elements to T or its subclasses, and lower-bounded wildcards `<? super T>` restricting elements to T or its superclasses. Core advantages: Compile-time type checking ensures safety, eliminates forced conversions, and allows code reuse through parameterized types. Considerations: Primitive types require wrapper classes, generics are non-inheritable, and type erasure prevents direct instantiation of T. Mastering generic parameters, wildcards, and collection applications effectively improves code quality.