解决 List 执行 remove 时报异常 java.lang.UnsupportedOperationException

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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()));