JAVA 文件按照指定格式切分成多个文件

按照自定义规则，拆分文件

1.测试文件路径：D://test.txt
2.截取规则content.substring(0,1);
3.第一个符合规则的字符串String lastA = "1";
4.输出路径D://" + lastA + ".txt

	public static void main(String[] args) {
        try {
            File file = new File("D://test.txt");
            InputStreamReader r = new InputStreamReader(new FileInputStream(file));
            BufferedReader reader = new BufferedReader(r);

            String content;
            String lastA = "1";
            StringBuffer sb = new StringBuffer("");
            do{
                content = reader.readLine();
                if(content == null){
                    //最后一次输出
                    File outFile = new File("D://" + lastA + ".txt");
                    OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(outFile));
                    writer.write(sb.toString());
                    writer.close();

                    break;
                }
                //注：你的截取规则
                String a = content.substring(0,1);

                if(a.equals(lastA)){
                    sb.append(content).append("\n");
                }else{
                    //标识改变，输出文件
                    File outFile = new File("D://" + lastA + ".txt");
                    OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(outFile));
                    writer.write(sb.toString());
                    //清空输出内容
                    sb = new StringBuffer("");
                    sb.append(content).append("\n");
                    writer.close();
                }
                lastA = a;

                System.out.println("=======");
            }while (true);

            r.close();
            reader.close();

        } catch (Exception e) {
            e.printStackTrace();
        }


    }

4.测试文件内容：

1 123456
1 1234567
2 123abc
2 abcd
3 abcd

上述文件会被切割成三个文件，分别是D://1.txt、D://2.txt、D://3.txt
文件内容同测试文件对应某行，前两行对应文件1.txt，3、4行对应文件2.txt，5行对应文件3.txt，以此类推