java stream Interface Collector＜T,A,R＞实例

Myth丶恋晨 2022-11-04 08:50 9阅读 0赞

package com;
    
    
    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;
    
    public class App2 { 
        public static void main(String[] args) { 
            List<String> list = new ArrayList<>();
            list.add("a");
            list.add("b");
            
            list.stream().collect(new Collector<String, Set<String>, Set<String>>() { 
                @Override
                public Supplier<Set<String>> supplier() { 
                    System.out.println("suppliier invoked!");
                    return HashSet::new;
                }
    
                @Override
                public BiConsumer<Set<String>, String> accumulator() { 
                    System.out.println("accmulator invoked!");
                    return Set::add;
                }
    
                @Override
                public BinaryOperator<Set<String>> combiner() { 
                    System.out.println("combiner invoked!");
                    return (set1, set2) -> { 
                        set1.addAll(set2);
                        return set1;
                    };
                }
    
                @Override
                public Function<Set<String>, Set<String>> finisher() { 
                    System.out.println("finisher invoked!");
                    return Function.identity();
                }
    
                @Override
                public Set<Characteristics> characteristics() { 
                    System.out.println("characteristics invoked");//没有任何限定
                    return new HashSet<>();
                }
            });
    
        }
    }

参考:  
[java8新特性(四) Collector（收集器）][java8_ Collector]  
[Java8中重要的收集器collector][Java8_collector]  
[JAVA8学习9-自定义收集器（Characteristics 使用说明）][JAVA8_9-_Characteristics]

[java8_ Collector]: https://blog.csdn.net/xiliunian/article/details/88773718
[Java8_collector]: http://www.voidcn.com/article/p-uflflvaw-bad.html
[JAVA8_9-_Characteristics]: https://blog.csdn.net/z_yemu/article/details/89401321