How to use Java generics

When using generics in Java, you can follow these steps:

1. Declare a generic class: Add generic parameters using angle brackets <> after the class name. For example, class MyClass { } represents a class with a generic parameter T.
2. When using generic classes, you specify the concrete type parameters when creating instances of the class. For example, MyClass myObj = new MyClass(); represents creating an instance of a generic class where the type parameter T is specified as String.
3. To declare a generic method, similar to declaring a generic class, use angle brackets <> to add generic parameters after the method name. For example, public void myMethod(T obj) { } represents a method with a generic parameter T.
4. 使用泛型方法：在调用方法时，可以根据需要指定具体的类型参数，也可以让编译器自动推断类型参数。例如，myMethod(“Hello”);表示调用myMethod方法并传递一个String类型的参数。
5. Generic wildcard: Sometimes, when unsure about the specific type of generic parameter, a wildcard ? can be used. For example, List myList = new ArrayList(); represents creating a generic list, but without specifying the exact type of elements in the list.
6. Generic constraints: The ‘extends’ keyword can be used to limit the type range of generic parameters. For example, public void myMethod(T obj) { } indicates that the generic parameter T must be of type Number or a subclass.

The above is a basic usage of generics in Java, which can increase code flexibility and safety by allowing for type checking during compile time to reduce runtime errors.