为什么不能通过下面代码获取“projectName”:String projectName = projectMap.get(projectId); projectCountVO.setName(projectName);

这可能是因为`projectMap`中不存在对应`projectId`的键值对，或者对应的`projectName`值为`null`。你可以先检查一下`projectMap`是否包含`projectId`键，如果包含的话再尝试获取`projectName`的值。另外，建议添加一些空值或不存在值的判断，避免出现空指针异常。例如：

if (projectMap.containsKey(projectId)) {
    String projectName = projectMap.get(projectId);
    if (projectName != null) {
        projectCountVO.setName(projectName);
    } else {
        // 处理 projectName 为空的情况
    }
} else {
    // 处理 projectMap 中不存在 projectId 的情况
}

相关问题

修改下面代码，根据“projectId”获取“projectName”：String projectName = projectMap.get(projectId); projectCondition.setProjectName(projectName);

Assuming that "projectMap" is a Map object with projectId as key and projectName as value, the code to retrieve the projectName based on the projectId would look like this:

String projectName = projectMap.get(projectId);
projectCondition.setProjectName(projectName);

This code retrieves the value (projectName) corresponding to the key (projectId) from the projectMap using the get() method. The retrieved projectName is then set in the projectCondition object using the setProjectName() method.

下面代码为何无法获取“projectname”：Map<String, String> projectMap = queryAllProject.stream().collect(Collectors.toMap(QueryAllProject::getId, QueryAllProject::getName)); // 遍历项目及对应的任务列表 for (Map.Entry<String, List<TaskTask>> projectTaskEntry : projectTaskMap.entrySet()) { projectId = projectTaskEntry.getKey(); ProjectCountVO projectCountVO = new ProjectCountVO(); projectCountVO.setId(projectId); // 根据projectId获取项目名称 String projectName = projectMap.get(projectId); projectCountVO.setName(projectName); //projectCondition.setProjectName(projectName); List<TaskTask> taskList = projectTaskEntry.getValue(); projectCountVO.setTaskCount(taskList.size()); Integer problemCount = CollectionUtil.isEmpty(taskList) ? 0 : taskList.stream().collect(Collectors.summingInt(task -> Optional.ofNullable(task.getProblemNum()).orElse(0))); projectCountVO.setProblemCount(problemCount); result.add(projectCountVO); } return result;

可能是因为 `queryAllProject` 中没有包含 `projectid` 对应的值，导致在 `projectMap` 中无法找到对应的项目名称。你可以添加一个空值判断，如下所示：

String projectName = projectMap.get(projectId);
if (projectName == null) {
    projectName = "";
}
projectCountVO.setName(projectName);

这样就能够避免 `NullPointerException` 的出现，并将未找到项目名称的情况视为一个空字符串。