Java Fundamentals Review-20 (generics)

1, because what type of elements in the collection can be stored. Causes the run-time classcastexception to be raised if a strong turn occurs. How to solve this problem? When you use a collection, you must explicitly specify the type of the elements in the collection. This approach is called: Generics.

2, the application of generics is divided into three kinds: the class containing the generic type, containing the generic interface, containing a generic method.

3. When generics are used, define the format: (1) modifier class name < variable representing generic type > {}

(2) Public <T> T[] toArray(t[] a) {}

(3) Modifier Interface interface Name < variable representing generic type > {}

4. What are the benefits of using generics?

A: The classcastexception of the runtime was transferred to the compile time and failed to compile. Avoid the trouble of type strong turn.

5, the use of generic wildcard environment: When the generic type cannot be determined, but to ensure the security of the code, this time with the generic wildcard <?> to ensure that the code compiled successfully.

Generic wildcard characters commonly used methods: (1) <? Extends a>//represents sub-class elements of Class A or class A

(2) <? Super a>//represents the parent element of Class A or class A

Java Fundamentals Review-20 (generics)