JAVA8-自定义Collector 自定义Collector实现Collector接口package com.example.study.java8.collector; import java.util.*; import java.util.function.BiConsumer; import java.util.function.BinaryOperator; import java.util.function.Function; import java.util.function.Supplier; import java.util.stream.Collector; /** * 自定义Collector * T:元素类型 * List<T>:要创建的类型 * List<T>:最后要返回的类型 */ public class ToListCollector<T> implements Collector<T, List<T>, List<T>> { private void log(final String log) { System.out.println(Thread.currentThread().getName()+"-"+log); } //一定时可变的supplier，不是固定值 @Override public Supplier<List<T>> supplier() { log("supplier"); return ArrayList::new; } //要进行的操作 @Override public BiConsumer<List<T>, T> accumulator() { log("accumulator"); return List::add; } //将结果整合 @Override public BinaryOperator<List<T>> combiner() { log("combiner"); return (list1,list2)->{ list1.addAll(list2); return list1; }; } //返回结果 @Override public Function<List<T>, List<T>> finisher() { log("finisher"); // return t->t; return Function.identity(); } //特征值:CONCURRENT-并行,UNORDERED-排序，IDENTITY_FINISH-入参就出参 @Override public Set<Characteristics> characteristics() { log("characteristics"); return Collections.unmodifiableSet(EnumSet.of(Characteristics.IDENTITY_FINISH, Characteristics.CONCURRENT)); } } 使用测试package com.example.study.java8.collector; import java.util.Arrays; import java.util.List; import java.util.stream.Collector; /** * 使用自定义Collector测试 */ public class CustomToListCollector { public static void main(String[] args) { String[] arrs = new String[]{"chinese","japanse","english","freach","Korean"}; //测试 //对应接口中的： //Supplier<A> supplier(), BiConsumer<A, T> accumulator(),Function<A, R> finisher(); Collector<String, List<String>, List<String>> collector = new ToListCollector<String>(); List<String> list = Arrays.stream(arrs).filter(s -> s.length() > 6).collect(collector); System.out.println(list); System.out.println("================================"); //parallelStream（），并行使用测试 List<String> parallelList = Arrays.asList(new String[]{"chinese", "japanse", "english", "freach", "Korean"}) .parallelStream() .filter(s -> s.length() > 6) .collect(collector); System.out.println(parallelList); } } 输出结果main-supplier main-accumulator main-combiner main-characteristics main-characteristics [chinese, japanse, english] ================================ main-characteristics main-characteristics main-supplier main-accumulator main-combiner main-characteristics main-characteristics [chinese, japanse, english]由于数据量少，并没有出现并行。