Shulou(Shulou.com)06/01 Report--

This article will explain in detail what the new features of Java5, Java6, Java 7, Java 8 are. The quality of the article is high, so Xiaobian shares it with you as a reference. I hope you have a certain understanding of relevant knowledge after reading this article.

Java51, Generics:

By referencing generics, it allows you to specify the types of elements in a collection, eliminating cast typing and the benefits of compile-time type checking.

Parameterized Type as parameter and return value, Generic is the cornerstone of vararg, annotation, enumeration, collection.

A. type-safe

Discard List, Map, use List, Map, add elements to them or use Iterator traversal, compile time can check for type errors for you

B. Method parameters and return values plus Type

Discard List, Map, Use List, Map

C. List = new ArrayList();String str = list.get(i);D. Type Wildcard?

Suppose we have a printList method that prints elements from a List, we want any List of type T to be printed, code:

public void printList(List list,PrintStream out)throws IOException{ for(Iterator i=list.iterator();i.hasNext();){ System.out.println(i.next.toString()); } }

What if wildcards? Let's make our parameter type too broad, we can change List and Iterator to List

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