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In this article, the editor introduces in detail "how to apply java generics". The content is detailed, the steps are clear, and the details are handled properly. I hope this article "how to apply java generics" can help you solve your doubts.

1. What is generics

Generics allow you to use an identity to represent the type of an attribute in a class or the return value and parameter type of a method when defining a class or interface. This type parameter will be determined when it is used (for example, inheriting or implementing this interface, declaring variables with this type, creating an object) (that is, passing in the actual type parameter, also known as the type argument).

Generics are a parameterized type.

2. Rules for the use of generics

Generics appear in JDK5.0 and cannot be used in previous versions

Generics need to be written in pairs.

The type of a generic type must be a reference type, not a basic data type.

If it is a basic data type, you must use its wrapper class. If there are multiple generic types, separate them with commas

3. Examples of generic applications

Example:

Public class DAO {private Map map = new HashMap (); public void save (String id,T entity) {map.put (id,entity);} public T get (String id) {return map.get (id);} public void update (String id,T entity) {map.put (id,entity);} public List list () {Collection values = map.values (); List list = new ArrayList () For (T value: values) {list.add (values);} return list;} public void delete (String id) {map.remove (id);}} public class DAOTest {public static void main (String [] args) {DAO userDAO = new DAO (); User user1 = new User (1LJ 12, "Zhang San"); User user2 = new User (2Jue 13, "Li Si") User user3 = new User (3jue 14, "Wang Wu"); userDAO.save ("1", user1); userDAO.save ("2", user2); userDAO.save ("3", user3); System.out.println (userDAO.get ("1")); userDAO.update ("1", new User (1Jing 18, "Zhang San")); List list = userDAO.list (); System.out.println (list) UserDAO.delete ("1"); System.out.println (userDAO.list ());}} read here, this article "how to apply java generics" has been introduced. If you want to master the knowledge points of this article, you still need to practice and use it before you can understand it. If you want to know more about related articles, welcome to follow the industry information channel.

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