需要额外过滤时重用流 - Java

Question

总之,以下代码意味着筛选第二个参数中的实体的第一个参数.如果在第二个参数中指定了"更改",则应该过滤较窄的结果.

当我运行它时,我得到一个错误'IllegalStateException:stream已被操作或关闭.

有没有办法可以重用相同的流？
我见过人们实现像Supplier这样的东西,但我认为这不适合这种情况.或者,我只是不熟悉它以了解我如何使用供应商.

/**
     * Filters through DocumentAuditEntityListing to find existence of the entities
     * ActionEnum, ActionContextEnum, LevelEnum, & StatusEnum.
     *
     * @param audits A list of audits to search
     * @param toFind The audit entities to find
     * @return If entities found, return DocumentAudit, else null
     */
    public DocumentAudit verifyAudit(DocumentAuditEntityListing audits, DocumentAudit toFind) {
        //Filter for proper entities
        Stream stream = audits.getEntities().stream().filter(doc -> (
                doc.getAction().equals(toFind.getAction())) &&
                doc.getActionContext().equals(toFind.getActionContext()) &&
                doc.getLevel().equals(toFind.getLevel()) &&
                doc.getStatus().equals(toFind.getStatus()));

        //If changes were specified, filter further.
        if (toFind.getChanges() != null){
            stream.filter(change -> (toFind.getChanges().contains(change)));
        }

        return (DocumentAudit) stream.findFirst().orElse(null);
    }

Answer 1

您需要使用分配结果流stream = stream.filter(change -> ...).

也使流类型安全(即Stream<DocumentAudit>).自Java 5以来,泛型一直存在,所以你没有借口使用原始类型.

        Stream<DocumentAudio> stream = audits.getEntities().stream()
            .filter(doc -> 
                doc.getAction().equals(toFind.getAction())) &&
                doc.getActionContext().equals(toFind.getActionContext()) &&
                doc.getLevel().equals(toFind.getLevel()) &&
                doc.getStatus().equals(toFind.getStatus());


        if (toFind.getChanges() != null){
            stream = stream.filter(change -> toFind.getChanges().contains(change));
        }

        return stream.findFirst().orElse(null);