Java 8 如何使用 lambda 表达式简化 for 循环

Question

我的代码中有这个方法，需要使用 java 8 表达式来简化和减少行。Lambda 可用于此目的，但如果没有列表作为输入似乎是不可能的。

  public ResourceUsage[] filterResourceUsages(ResourceUsage[] resourceUsages, int role, int includeResourceType)
    throws SpiderException
  {
    ArrayList<ResourceUsage> filteredResourceUsages = new ArrayList<>();

    String[] ids = new String[resourceUsages.length];
    for (int i = 0; i < resourceUsages.length; i++)
    {
      ids[i] = resourceUsages[i].resource;
    }

    ResourceData[] resourceData = resourceToolkitAdapter.getData(ids);

    for (int i = 0; i < resourceData.length; i++)
    {
      if (resourceUsages[i].role == role && resourceData[i].basic.type == includeResourceType)
      {
        filteredResourceUsages.add(resourceUsages[i]);
      }
    }
    return filteredResourceUsages.toArray(new ResourceUsage[filteredResourceUsages.size()]);
  }

我试过使用resourceUsages.forEach(resourceUsages.resource-> do something);但没有列表作为输入似乎是不可能的。

有没有办法简化这段代码？

Answer 1

这是原始数组和批处理解决方案：

public ResourceUsage[] filterResourceUsages(ResourceUsage[] resourceUsages, int role, int includeResourceType)
        throws SpiderException {

    String[] ids = Stream.of(resourceUsages)
            .map(ResourceUsage::getResource)
            .toArray(String[]::new);
    Map<String, ResourceData> resourceDataMap = Stream.of(resourceToolkitAdapter.getData(ids))
            .collect(Collectors.toMap(ResourceData::id, Function.identity()));
    return Stream.of(resourceUsages)
            .filter(usage -> usage.role == usage)
            .filter(resourceDataMap::containsKey)
            .filter(usage -> resourceDataMap.get(usage.resource).basic.type == includeResourceType)
            .toArray(ResourceUsage[]::new);
}