2020了你还不会java8新特性？（八）流源构造代码分析与总结

记录下来，然后给别人再讲，你就掌握了。

学完之后忘记了怎么办？记录下来。 笔记 博客。 死记硬背是没有任何用的。

ReferencePipeline

/**
 * Abstract base class for an intermediate pipeline stage or pipeline source
 * stage implementing whose elements are of type {@code U}.
 */
//引用管道   
//ReferencePipeline  表示流的源阶段与中间阶段。
//ReferencePipeline.head表示流中的源阶段。
 abstract class ReferencePipeline<P_IN, P_OUT>
        extends AbstractPipeline<P_IN, P_OUT, Stream<P_OUT>>
        implements Stream<P_OUT>  {  
 }

AbstractPipeline

/**
 * Abstract base class for "pipeline" classes, which are the core
 * implementations of the Stream interface and its primitive specializations.
 * Manages construction and evaluation of stream pipelines.
 *  
 * <p>An {@code AbstractPipeline} represents an initial portion of a stream
 * pipeline, encapsulating a stream source and zero or more intermediate
 * operations.  The individual {@code AbstractPipeline} objects are often
 * referred to as <em>stages</em>, where each stage describes either the stream
 * source or an intermediate operation.
 流管道的初始的一部分。
 *
 * <p>A concrete intermediate stage is generally built from an
 * {@code AbstractPipeline}, a shape-specific pipeline class which extends it
 * (e.g., {@code IntPipeline}) which is also abstract, and an operation-specific
 * concrete class which extends that.  {@code AbstractPipeline} contains most of
 * the mechanics of evaluating the pipeline, and implements methods that will be
 * used by the operation; the shape-specific classes add helper methods for
 * dealing with collection of results into the appropriate shape-specific
 * containers.
 *避免自动拆箱和装箱操作。
 * <p>After chaining a new intermediate operation, or executing a terminal
 * operation, the stream is considered to be consumed, and no more intermediate
 * or terminal operations are permitted on this stream instance.
 * 当链接完一个新的中间操作或者执行了终止操作之后， 这个流被认为被消费了。不允许再被操作了。
 * @implNote
 * <p>For sequential streams, and parallel streams without
 * <a href="package-summary.html#StreamOps">stateful intermediate
 * operations</a>, parallel streams, pipeline evaluation is done in a single
 * pass that "jams" all the operations together.  For parallel streams with
 * stateful operations, execution is divided into segments, where each
 * stateful operations marks the end of a segment, and each segment is
 * evaluated separately and the result used as the input to the next
 * segment.  In all cases, the source data is not consumed until a terminal
 * operation begins.
  只有终止操作开始的时候，源数据才会被消费。
 * @param <E_IN>  type of input elements
 * @param <E_OUT> type of output elements
 * @param <S> type of the subclass implementing {@code BaseStream}
 * @since 1.8
 */
abstract class AbstractPipeline<E_IN, E_OUT, S extends BaseStream<E_OUT, S>>
        extends PipelineHelper<E_OUT> implements BaseStream<E_OUT, S> {
}

内部类，和lambda表达式之间的关系。

本质上 内部类和lambda不是一回事。只是能完成相同的操作。

lambda不是匿名内部类的语法糖，或者说是缩写。是一种新的形式。

public class LambdaTest {
    //内部类，和lambda表达式之间的关系。
    Runnable r1 = () -> System.out.println(this); // this表示当前类的对象

    //匿名内部类
    Runnable r2 = new Runnable() {  //
        @Override
        public void run() {
            System.out.println(this);
            // this 表示匿名内部类的对象
        }
    };


    public static void main(String[] args) {
        LambdaTest lambdaTest = new LambdaTest();

        Thread t1 = new Thread(lambdaTest.r1);
        t1.start();

        System.out.println("- - -- - ");

        Thread t2 = new Thread(lambdaTest.r2);
        t2.start();
        //输出结果。
        //com.sinosoft.lis.test.LambdaTest@62661526
        //com.sinosoft.lis.test.LambdaTest$1@59a30351
    }

}

使用了模板方法模式。

流是惰性的，是延迟操作的。遇到终止操作时，才会执行操作。

TerminalOp。 终止操作的接口类。

终止操作 只有四种类型， findOp foreachOp matchOp reduceOp

PipelineHelper

stream中间操作与终止操作层次体系分析与设计思想分析

中间操作

BaseStream -》 AbStractpipeline -》ReferencePipeline -》 Head || StatelessOP || statefulOp

最顶层的源 很多源的成员变量 管道 构造流源 无状态的中间操作 有状态的中间操作

流是惰性的，是延迟操作的。遇到终止操作时，才会执行操作。再没有终止操作之前，在整合中间操作（Sink）。

终止操作

TerminalOp -》 FindOp || ForeachOp || MatchOp || reduceOp

最顶层的

TerminalSink

终止的饮水槽。

标签：AbstractPipeline,pipeline,code,stream,流源,intermediate,2020,操作,java8
来源： https://www.cnblogs.com/wobushitiegan/p/12174438.html