The beginning of this chapter introduced the idea of writing code that can be applied as generally as possible. To do this, we need ways to loosen the constraints on the types that our code works with, without losing the benefits of static type check…

​Ordinary classes and methods work with specific types: either primitives or class types. If you are writing code that might be used across more types, this rigidity can be overconstraining. One way that object-oriented languages allow generalization…

2.4 The Get and Put Principle Get and Put Principle: 用于取对象的泛型集合,声明为 <? extends T> 用于存对象的泛型集合,声明为 <? super T> 如果同时存取,那么还是老老实实的用< T>吧 注意: void put(List<? extends Number> nums){ nums.add(?) } 上面代码中'?'处只能放入null值,因为你并不能确定nums具体是什么类型的Lis…

2.3 Wildcards with super 这里就直接拿书上的例子好了,这是Collections里面的一个方法: public static <T> void copy(List<? super T> dst,List<? extends T> src){ for(int i = 0; i < src.size(); i++){ dst.set(i,src.get(i)); } } 其中<? super T> 表示T以以及T的父类,java的泛…

2.2 Wildcards with extends 前面介绍过List<Integer>不是List<Number>的子类,即前者不能替换后者, java使用? extends [classname]语法,即List<Integer> 可以替换 List<? extends Number>. 看两段代码: package java_generics_collections.chap2; import org.junit.Test; import java.…

2.1 子类化以及替换原理 为什么List<Integer> 不是List<Number> 的子类? 首先看下面的代码,这段代码是编译不过的 package java_generics_collections.chap2; import org.junit.Test; import java.util.ArrayList; import java.util.List; /** * Created by jintaox on 2016/3/21. */ public class Te…

8.1 Take Care when Calling Legacy Code 通常,泛型都是在编译时检查的,而不是运行时.便意识检查可以提早通知错误,而不至于到运行时才出问题. 但有时后编译时检查不一定就坚不可摧,因为有时我们在运行时才能之道具体类型. (唉,翻译水平有限,还是看代码吧) package java_generics_collections.chap08; import java.util.ArrayList; import java.util.List; /** * Create…

Flink uses a lot of generics programming, which is an executor Framework with cluster of executor having a lot of thread for task by RPC communication(Actor System). The data and the process of data are defined by user. Event-Driven == Callback funct…

原文地址:http://www.journaldev.com/122/java-concurrenthashmap-example-iterator#comment-27448 Today we will look into Java ConcurrentHashMap Example. If you are a Java Developer, I am sure that you must be aware of ConcurrentModificationException that com…

Generics The term "generic" means "pertaining or appropriate to large groups of classes." While using someone else's generic type is fairly easy, when creating your own you will encounter a number of surprises. Comparison with C++ Unde…