Master Java Generics

Introduction to Java Generics

• Java Generics were introduced in J2SE 5 to ensure type-safe objects and detect bugs at compile time.
• Before Generics, any type of object could be stored in a collection, but with Generics, only a specific type of object can be stored.
• Generics ensure type-safety, and there is no need for typecasting the object.
• Compile-time checking is done to avoid any problems at runtime.
• The syntax to use generic collection is ClassOrInterface<Type>.
• The ArrayList class is used in an example to demonstrate the use of Generics in Java.
• Generics can be used with any collection class, such as LinkedList, HashSet, TreeSet, HashMap, Comparator, etc.
• A generic class can refer to any type, and T type parameter is used to create a generic class of a specific type.
• Type parameters naming conventions are important to learn generics thoroughly.
• A generic method can be created that can accept any type of arguments, but its scope is limited to the method in which it is declared.
• Wildcard in Java Generics is represented by the ? symbol, which means any type.
• Upper and lower bounded wildcards are used to decrease the restrictions on a variable and to restrict the unknown type to a specific type or supertype.

Understanding Java Generics

• Java is type safe, meaning that variables must be declared with their type before use
• Collection APIs in Java allow for the storage of any type of value, which can lead to type safety issues
• Generics in Java allow for the specification of the type of element to be stored in a collection at compile time
• The syntax for specifying the type of element in a collection is to use angle brackets and the type name, such as <Integer>
• Using generics ensures type safety by allowing for errors to be caught at compile time instead of runtime
• Generics are implemented using the symbol 'T' to represent the type of element
• The 'T' can be replaced with any class, including custom classes
• Generics only support classes, not primitive data types like int or float
• Bounded types can be used to restrict the type of element that can be stored in a collection, such as <T extends Number> to only allow for Number and its subclasses
• The syntax for accepting a list with a bounded type is to use a wildcard with the keyword 'extends', such as <? extends Number>
• The syntax for accepting a list with a super type is to use a wildcard with the keyword 'super', such as <? super Integer>
• Using generics in Java allows for type safety and more efficient error handling.