读取一个文本文件，并使用java代码从其中仅选择2-3列

Question

我有一个文本文件，上面写着

18 8 307 130 3504 12 70 1 10

15 8 350 165 3693 11 70 1 10

18 8 318 150 3436 11 70 1 10

16 8 304 150 3433 12 70 1 10

17 8 302 140 3449 10 70 1 10

其中每个值由单个空格分隔。有没有什么算法可以让我们只选择特定的列，而不是所有的列，并将它们写到另一个文件中？

对于ex。我想在第一列，第二列，第五列和第六列工作，所以我的代码应该选择这些列中的所有属性，并在另一个文件中重写它们。

Answer 1

算法可以是这样的。

1-First calculate number of rows and columns exists in file by any method.
int col,row;

2-Create a two dimensional matrix 
int matrix[row][col]
and copy all elements from file to matrix.

3-Now you have the matrix you can access any column of your choice and can perform any operation in this.

这可以更精致，但想法应该是这样的。

Answer 2

答案：

static final String s = "18 8 307 130 3504 12 70 1 10 \n" +
                       "15 8 350 165 3693 11 70 1 10 \n" +
                       "18 8 318 150 3436 11 70 1 10 \n" +
                       "16 8 304 150 3433 12 70 1 10 \n" +
                       "17 8 302 140 3449 10 70 1 10";

public static void main(String... str) {
    List<String> lines = Arrays.asList(s.split("\\n"));
    StringBuilder sb = new StringBuilder();
    for (String s : lines) {
        String[] tempStr = s.split("\\s");
        appendRightColumns(sb, tempStr);
    }

    writeToFile(sb);
}

private static void writeToFile(StringBuilder sb) {
    BufferedWriter writer = null;
    try {
        writer = new BufferedWriter(new FileWriter("C:\\your_file.txt"));
        writer.write(sb.toString());
    } catch (IOException e) {
    } finally {
        try {
            if (writer != null)
                writer.close();
        } catch (IOException e) {
        }
    }
}

private static void appendRightColumns(StringBuilder sb, String[] tempStr) {
    sb.append(tempStr[0]);
    sb.append(" ");
    sb.append(tempStr[1]);
    sb.append(" ");
    sb.append(tempStr[4]);
    sb.append(" ");
    sb.append(tempStr[5]);
    sb.append("\n");
}

Answer 3

请尝试以下操作：

public void read() throws FileNotFoundException, IOException
{
    FileInputStream fstream = new FileInputStream("screendump");
    DataInputStream in = new DataInputStream(fstream);
    BufferedReader br = new BufferedReader(new InputStreamReader(in));
    String strLine;
    //Read File Line By Line
     while ((strLine = br.readLine()) != null)   {
     processLine(strLine );
    }
}
protected void processLine(String aLine){
//use a second Scanner to parse the content of each line 
Scanner scanner = new Scanner(aLine);

if (scanner.hasNext()){
  //assumes the line has a certain structure
    switch(i)
    {
        case 1:
         //store in string id = scanner.next().trim(); 
         break;

        case 2: 
         //store in string id+ = scanner.next().trim();
         break;

        case 3:
         break;

        case 4:
         break;

        case 5:
         //store in string id+ = scanner.next().trim();
         break;

        case 6: 
         //store in string id+ = scanner.next().trim();
         break;

        default:
         break;