/** * 将一个指定类型对象的集合按照自定义的一个操作分组; 每组对应一个List、最终返回结果类型是:List> * * @param */ static class GroupToList implements Collector>, List>> { /** * 集合中对象两两比较,满足自定义的条件(operation结果返回true),便将这两个元素分为一组 */ private BiFunction operation; public GroupToList(BiFunction operation) { super(); this.operation = operation; } @Override public BiConsumer>, T> accumulator() { return (c, t) -> { boolean added = false; for (List cc : c) { for (T ccc : cc) { if (operation.apply(ccc, t)){ cc.add(t); added = true; } break; } if (added) break; continue; } if (!added) { ArrayList list = new ArrayList(); list.add(t); c.add(list); } }; } @Override public Set characteristics() { /* Set emptySet = Collections.emptySet(); */ return Collections.unmodifiableSet(EnumSet.of(Characteristics.IDENTITY_FINISH)); } @Override public BinaryOperator>> combiner() { return (l1,l2) -> {l2.addAll(l1); return l2;}; } @Override public Function>, List>> finisher() { return p -> p; } @Override public Supplier>> supplier() { return () -> new ArrayList>(); } }
Java8自定义条件让集合分组