IO

主要使用：文件读写

文件读：FileUtils.readLines
文件写：FileUtils.writeLines

下面是一个实际的例子，一共涉及三个文件：

1. 文件1：cer-userid-technicianid.txt 所有认证技师的userId，technicianId 数据格式，第一列userId，第二列technicianId，tab键隔开

   178479650 2134
   666951 193
   51265592 1461
   145921104 76290
   720872160 2438

2. 文件2：technicianid-yuan.txt 所有报名参加活动的technicianId 数据格式，只有一行，逗号分隔

   1348,95239,95243,95244,95245,95246,95248

3. 文件3：UserId-TechnicianId-result.txt 输出的结果文件，求所有报名参加活动的技师中已认证技师的userId，technicianId。

代码如下：

@Test
public void test32() throws IOException {
    final List<String> lines = FileUtils.readLines(new File("/Users/chenjp/Documents/learn/work/file/cer-userid-technicianid.txt"), "utf-8");

    final List<String> technicianIdList = FileUtils.readLines(new File("/Users/chenjp/Documents/learn/work/file/technicianid-yuan.txt"), "utf-8");

    final File result = new File("/Users/chenjp/Documents/learn/work/file/UserId-TechnicianId-result.txt");

    final ArrayList<Integer> technicianIds = Lists.newArrayList(FluentIterable.from(Splitter.on(",").omitEmptyStrings().splitToList(technicianIdList.get(0))).transform(new Function<String, Integer>() {
        @Override
        public Integer apply(String input) {
            return NumberUtils.toInt(input);
        }
    }));

    Lists.newArrayList(FluentIterable.from(lines).transform(new Function<String, String>() {
        @Override
        public String apply(String input) {
            try {
                if (StringUtils.isBlank(input)) {
                    return null;
                }
                List<String> list = Splitter.onPattern("\\s").omitEmptyStrings().splitToList(input);
                if (!technicianIds.contains(NumberUtils.toInt(list.get(1)))) {
                    System.err.println(String.format("bad technicianId[%s]", list.get(1)));
                    return null;
                }
                System.out.println(String.format("write to result file[%s]", input));
                FileUtils.writeLines(result, "utf-8", Lists.newArrayList(input), true);
            } catch (IOException e) {
                e.printStackTrace();
            }
            return input;
        }
    }));
}

结果自体会