首頁猿問使用 lambda 時處理空指針

使用 lambda 時處理空指針

Java

慕桂英546537 2022-12-21 14:44:47

nullPointerException除非e.getKey()返回，否則下面的代碼會得到嗎nullMap<Integer, Optional<SecurityAttributeChange>> spnCreationDetails;Optional.ofNullable(spnCreationDetails.get(e.getKey()).orElse(new SecurityAttributeChange()).getNewAttribute()) .orElse(new SecurityAttr()) .getUserName());我在這一行中遇到了 NPE，是否可以調(diào)試它？我知道spnCreationDetails.get(e.getKey())返回 null，我null在這里處理時遺漏了什么嗎？- 編輯這是幾乎完整的方法，它將有助于提供有關如何重構它以使其可讀的輸入。private void updateAuditFields(List<SecurityAttributeChange> securityChanges, Map<Integer, Map<String, Object>> result) { Map<Integer, Optional<SecurityAttributeChange>> spnModificationDetails = ... Map<Integer, Optional<SecurityAttributeChange>> spnCreationDetails = ... result.entrySet().stream().forEach(e -> { e.getValue() .put("userIdLastChanged", Optional.ofNullable(Optional.ofNullable(spnModificationDetails.get(e.getKey())) .orElse(Optional.of(new SecurityAttributeChange())) .get() .getNewAttribute()).orElse(new SecurityAttr()).getUserName()); e.getValue() .put("lastChangedDatetime", Optional.ofNullable(Optional.ofNullable(spnModificationDetails.get(e.getKey())) .orElse(Optional.of(new SecurityAttributeChange())) .get() .getNewAttribute()).orElse(new SecurityAttr()).getKnowledgeBeginDate()); e.getValue() .put("userIdCreated", Optional.ofNullable( Optional.ofNullable(spnCreationDetails.get(e.getKey())).orElse(Optional.of(new SecurityAttributeChange())).get().getNewAttribute()) .orElse(new SecurityAttr()) .getUserName()); });}

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1 回答

泛舟湖上清波郎朗

TA貢獻1818條經(jīng)驗獲得超3個贊

如果spnCreationDetails.get(e.getKey())可以為空，您可能需要：

Optional.ofNullable(spnCreationDetails.get(e.getKey()))
        .orElse(new SecurityAttributeChange())
        .getNewAttribute()
        .orElse(new SecurityAttr())
        .getUserName();

iespnCreationDetails.get(e.getKey())應該用Optional.

編輯：看到您的評論，spnCreationDetails.get(e.getKey())可以返回 anull或 an Optional<SecurityAttributeChange>，因此最好只將 thenull轉(zhuǎn)換為 new Optional：

spnCreationDetails.getOrDefault(e.getKey(),Optional.empty())
                  .orElse(new SecurityAttributeChange())
                  .getNewAttribute()
                  .orElse(new SecurityAttr())
                  .getUserName();

反對回復 2022-12-21