Java简单实现本地文件读写操作

 1 public class Test {
 2 
 3     public static void main(String[] args) {
 4         boolean isFirst = true;
 5         try {
 6             File file = new File("E:\\index_all.txt");
 7             File outFile = new File("E:\\index.txt");
 8             if (file.isFile() && file.exists()) { //判断文件或目录是否存在
 9                 InputStreamReader reader = new InputStreamReader(new FileInputStream(file), "utf-8");
10                 BufferedReader bufferedReader = new BufferedReader(reader);
11                 OutputStreamWriter writer = new OutputStreamWriter(new FileOutputStream(outFile), "gbk");
12                 BufferedWriter bufferedWriter = new BufferedWriter(writer);
13                 OutputStreamWriter writer2017 = new OutputStreamWriter(new FileOutputStream(outFile), "gbk");
14                 BufferedWriter bufferedWriter2017 = new BufferedWriter(writer);
15                 String lineTxt = null;
16                 List<String> list = new ArrayList<>();
17                 while ((lineTxt = bufferedReader.readLine()) != null) {
18                     System.out.println(lineTxt);
19                     list.add(lineTxt.replace(" ", ","));
20 //                    bufferedWriter.write(lineTxt+"\r\n");
21                 }
22                 bufferedWriter.write(list.get(0).replace(",", " ") + "\tavg\r\n");
23 
24                 String[] arr = new String[list.size()];
25                 arr = list.toArray(arr);
26                 for (int i = 1; i < arr.length; i++) {
27                     String[] line = arr[i].split(",");
28                     String[] line2017 = arr[0].split(",");
29                     double avg = 0, sum = 0;
30                     /*int a = 0;
31                     for (int j = 9; j < line.length; j++) {
32                         if (line[j].length() > 0 && !line[j].startsWith("-999")) {
33                             sum += Double.valueOf(line[j]);
34                             a += 1;
35                         }
36                     }
37                     avg = sum / a;*/
38                     avg = getAvg(line);
39                     bufferedWriter.write(list.get(i).replace(",", " ") + "\t" + String.format("%.3f", avg) + "\r\n"); //保留3位小数
40                     bufferedWriter.flush(); //将缓冲区的内容输出
41 
42                     // 计算2017年每个指数的方差并输出成文本
43                     double powAvg = 0, powSum = 0;
44                     if (line[4].startsWith("2017")) {
45                         if (isFirst) {
46                             bufferedWriter2017.write("\r\n\r\n" + line2017[3] + "\t平均值" + "\t方差\r\n");
47                             isFirst = false;
48                         }
49                         double avg2017 = getAvg(line);
50                         int p = 0;
51                         for (int j = 9; j < line.length; j++) {
52                             if (line[j].length() > 0 && !line[j].startsWith("-999")) {
53                                 powSum += Math.pow((Double.valueOf(line[j]) - avg2017), 2); //计算平方和
54                                 p += 1;
55                             }
56                         }
57                         powAvg = powSum / p; //计算方差
58                         bufferedWriter2017.write(line[4] + "\t" + String.format("%.3f", avg) + "\t" + String.format("%.3f", powAvg) + "\r\n");
59                     }
60                 }
61                 bufferedWriter.flush(); //将缓冲区的内容输出
62                 bufferedWriter2017.flush();
63                 bufferedWriter.close(); //①先关BufferedWriter 
64                 bufferedWriter2017.close();
65                 writer.close(); //②后关OutputStreamWriter 
66                 writer2017.close();
67                 bufferedReader.close();
68                 reader.close();
69             } else {
70                 System.out.println("找不到指定的文件");
71             }
72         } catch (Exception e) {
73             System.out.println("读取文件内容出错");
74             e.printStackTrace();
75         }
76     }
77 
78     private static double getAvg(String[] line) {
79         double sum = 0;
80         int a = 0;
81         for (int j = 9; j < line.length; j++) {
82             if (line[j].length() > 0 && !line[j].startsWith("-999")) {
83                 sum += Double.valueOf(line[j]);
84                 a += 1;
85             }
86         }
87         return sum / a;
88     }
89 }