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一、情况描述
报错如题：
java.lang.UnsupportedOperationException: nullat java.util.Collections$UnmodifiableCollection.removeAll(Collections.java:1068)
报错行定位到下图红框中这行：
代码如下（只是单纯的想 2 个集合求差集）：
List<WorkWeight> removeList = Lists.newArrayList();workWeightsList.forEach((workWeight -> {if (!employeeId.equals(workWeight.getApproverId()) && workWeight.getEmployeeId().equals(employeeId)) { // 当前人提交的不由自己审批的数据removeList.add(workWeight);}}));if (!CollectionUtils.isEmpty(removeList)) { workWeightsList.removeAll(removeList); // 这行报错}
二、解决办法
用 ArrayList 把集合 workWeightsList 再组装，如下图：
代码：
List<WorkWeight> removeList = Lists.newArrayList();workWeightsList.forEach((workWeight -> {if (!employeeId.equals(workWeight.getApproverId()) && workWeight.getEmployeeId().equals(employeeId)) { // 当前人提交的不由自己审批的数据removeList.add(workWeight);}}));if (!CollectionUtils.isEmpty(removeList)) {workWeightsList = new ArrayList<WorkWeight>(workWeightsList); // 改写这一行workWeightsList.removeAll(removeList);}return new Payload(new PageImpl(workWeightsList, pageable, result.getTotalElements()));
三、这样改写的原因参见：
UnsupportedOperationException报错原因解说
参考：https://www.jianshu.com/p/7f718d900111
