#vulnerable code 
                                private List<GroupState> decode(byte[] bs, Charset charset) throws IOException {
        // 获取对象转换定义
        ObjectMataData objectMataData = FdfsParamMapper.getObjectMap(GroupState.class);
        int fixFieldsTotalSize = objectMataData.getFieldsFixTotalSize();
        if (bs.length % fixFieldsTotalSize != 0) {
            throw new IOException("byte array length: " + bs.length + " is invalid!");
        }
        // 计算反馈对象数量
        int count = bs.length / fixFieldsTotalSize;
        int offset = 0;
        List<GroupState> results = new ArrayList<GroupState>(count);

        for (int i = 0; i < count; i++) {
            byte[] one = new byte[fixFieldsTotalSize];
            System.arraycopy(bs, offset, one, 0, fixFieldsTotalSize);
            results.add(FdfsParamMapper.map(one, GroupState.class, charset));
            offset += fixFieldsTotalSize;
        }

        return results;
    } 
                            #location 4 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                private List<GroupState> decode(byte[] bs, Charset charset) throws IOException {
        // 获取对象转换定义
        ObjectMetaData objectMetaData = FdfsParamMapper.getObjectMap(GroupState.class);
        int fixFieldsTotalSize = objectMetaData.getFieldsFixTotalSize();
        if (bs.length % fixFieldsTotalSize != 0) {
            throw new IOException("byte array length: " + bs.length + " is invalid!");
        }
        // 计算反馈对象数量
        int count = bs.length / fixFieldsTotalSize;
        int offset = 0;
        List<GroupState> results = new ArrayList<GroupState>(count);

        for (int i = 0; i < count; i++) {
            byte[] one = new byte[fixFieldsTotalSize];
            System.arraycopy(bs, offset, one, 0, fixFieldsTotalSize);
            results.add(FdfsParamMapper.map(one, GroupState.class, charset));
            offset += fixFieldsTotalSize;
        }

        return results;
    }