Java8函数式编程接口:Consumer、Supplier、Function、Predicate_综合

开宗明义

java8的一个新特性就是在java.util.function中提供了四个函数式编程接口，分别是Consumer、Supplier、Function、Predicate。

其中，

consumer即消费接口，传入一个参数，并对其进行相应的操作（有点类似于lambda表达式）；
supplier即供给接口，可以传入数据，作为一个容器；
function即方法接口，主要是用作数据类型之间的转换；
predicate即判断接口，传入参数，而后返回判断的结果true/false；

接下来仔细瞅瞅这四种接口的源码以及怎么使用它们。

庖丁解牛

consumer

源码

Consumer接口的源码只有两个方法，一个方法用来接收入口参数，另外一个是为了实现流式操作：

@FunctionalInterface
public interface Consumer<T> {
       
<span class="token comment">/***接收一个泛型入参*/</span>
<span class="token keyword">void</span> <span class="token function">accept</span><span class="token punctuation">(</span><span class="token class-name">T</span> t<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment">/*** 是指在进行这个consumer之后，在将结果送进另外一个consumer，* 从而实现consumer的流式操作(一个接一个地进行)*/</span>
<span class="token keyword">default</span> <span class="token class-name">Consumer</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token class-name">T</span><span class="token punctuation">&gt;</span></span> <span class="token function">andThen</span><span class="token punctuation">(</span><span class="token class-name">Consumer</span><span class="token generics"><span class="token punctuation">&lt;</span><span class="token operator">?</span> <span class="token keyword">super</span> <span class="token class-name">T</span><span class="token punctuation">&gt;</span></span> after<span class="token punctuation">)</span> <span class="token punctuation">{<!-- --></span><span class="token class-name">Objects</span><span class="token punctuation">.</span><span class="token function">requireNonNull</span><span class="token punctuation">(</span>after<span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token keyword">return</span> <span class="token punctuation">(</span><span class="token class-name">T</span> t<span class="token punctuation">)</span> <span class="token operator">-&gt;</span> <span class="token punctuation">{<!-- --></span> <span class="token function">accept</span><span class="token punctuation">(</span>t<span class="token punctuation">)</span><span class="token punctuation">;</span> after<span class="token punctuation">.</span><span class="token function">accept</span><span class="token punctuation">(</span>t<span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span>