java - 如何在嵌套 for 循环中重用用于 for 循环第一级的变量

Question

有人可以告诉我如何在 forEach 中重用 rootOpt 对象。有什么办法可以重用这个变量吗？当我在 forEach 中写入 rootOpt.getChildOptions() 时，出现以下消息“无法解析符号 rootOpt”。请在下面找到我所做的: 我尝试使用流重写下面的 for 循环。谢谢

opts.stream()
                .flatMap(rootOpt -> rootOpt.getChildOptions().stream())
                .forEach(subOpt -> {
                    if (subOpt.getOptLogic() != null && subOpt.getOptLogic().getCant() != null && !"".equals(subOpt.getOptLogic().getCant())) {
                        String[] oldCHs = subOpt.getOptLogic().getCant().split("( )");
                        OptionList samePriceSibs = getSamePriceS(rootOpt.getChildOptions(), subOpt);
                        for (String ch : oldCHs) {
                            Option chRootOpt = childOptCodeToParentOptMap.get(ch.toUpperCase());
                            if (chRootOpt != null) {
                                if (!DoesVariableOptionsCompletelyExcludeOther(samePriceSibs, chRootOpt.getChildOptions())) {
                                    List<OptionList> tmp = new ArrayList<OptionList>();
                                    tmp.add(samePriceSibs);
                                    tmp.add(chRootOpt.getChildOptions());
                                    optionsPairsToRemoveCHs.add(tmp);
                                }
                            }
                        }
                    }
                });

            for (Option rootOpt : opts) {
                for (Option subOpt : rootOpt.getChildOptions()) {
                    if (subOpt.getOptLogic() != null && subOpt.getOptLogic().getCant() != null && !"".equals(subOpt.getOptLogic().getCant())) {
                        String[] oldCHs = subOpt.getOptLogic().getCant().split("( )");
                        OptionList samePriceSibs = getSamePriceS(rootOpt.getChildOptions(), subOpt);
                        for (String ch : oldCHs) {
                            Option chRootOpt = childOptCodeToParentOptMap.get(ch.toUpperCase());
                            if (chRootOpt != null) {
                                if (!DoesVariableOptionsCompletelyExcludeOther(samePriceSibs, chRootOpt.getChildOptions())) {
                                    List<OptionList> tmp = new ArrayList<OptionList>();
                                    tmp.add(samePriceSibs);
                                    tmp.add(chRootOpt.getChildOptions());
                                    optionsPairsToRemoveCHs.add(tmp);
                                }
                            }
                        }
                    }
                }
            }

Answer 1

rootOpt 的范围以右括号结束。 你可以这样写

opts.stream().forEach(rootOpt ->
  rootOpt.getChildOptions().stream().forEach(subOpt -> {
    ...
  });
);

然而，流并不是真正旨在简单地替换 for 循环。使用它们的更规范的方式是这样的。

Stream<List<OptionList>> optionsPairsToRemoveCHs = opts.stream()
  .flatMap(rootOpt ->
    rootOpt.getChildOptions().stream()
           .filter(subOpt -> subOpt.getOptLogic() != null && subOpt.getOptLogic().getCant() != null && !"".equals(subOpt.getOptLogic().getCant()))
           .flatMap(subOpt -> {
              String[] oldCHs = subOpt.getOptLogic().getCant().split("( )");
              OptionList samePriceSibs = getSamePriceS(rootOpt.getChildOptions(), subOpt);
              return Stream.of(oldCHs)
                           .map(ch -> childOptCodeToParentOptMap.get(ch.toUpperCase()))
                           .filter(chRootOpt -> chRootOpt != null && !DoesVariableOptionsCompletelyExcludeOther(samePriceSibs, chRootOpt.getChildOptions()))
                           .map(chRootOpt -> Arrays.asList(samePriceSibs, chRootOpt.getChildOptions()));
           })
  );

不过我没有测试该代码。另外，按照迈克的建议将其重构为几种方法将有助于使其更易于阅读。