模式仅通过短字符串找不到行

Question

I have a file in the following pattern:

100:5,3

50:10,3

2:20,15

with NO free line inbetween (just to kill some misunderstandings)

I want to find a line that starts with a Input (lets say 50) , and i dont know the other two values yet. IF i find a line that starts with 50, i want to get the other two values and change them according to other stuff. lets say i want to rewrite that line into 50:11,4. IF i dont find a line starting with a input (lets say 40) i want to create a new line that looks like this : 40:1,0.

sofar i dug through Patterns, and my current state is this:

        Pattern p = Pattern.compile("(d\\+):(\\d+),(\\d+)");
        String inputString = Integer.toString(""+someValue+":(\\d+),(\\d+)";
        Matcher m = p.matcher(inputString);
        m.find();

        if (m.matches){  and so on  }

EDIT:

And how do i link the Matcher to a File?

Answer 1

For ease I used in my code FileUtils from Apache commons that you can get with

compile 'org.apache.commons:commons-io:1.3.2

You can now use a method like this

private void processFile(File file, int index, int x, int y) throws Exception{
    // load the file lines in an array
    ArrayList<String> lines = (ArrayList<String>)FileUtils.readLines(file);

    if(lines == null)
        return;

    // create the patter to match the required row
    Pattern p = Pattern.compile(index + ":(\\d+),(\\d+)");
    boolean found = false;
    // loop the lines to find the one we want
    for(int i = 0; i < lines.size(); i++){
        Matcher m = p.matcher(lines.get(i));
        m.find();
        if(m.matches()){
            // when we find it we change it to what we need
            lines.set(i, index + ":" + x + "," + y);
            // we mark that we found it and don't need to add it at the end
            found = true;
            break;
        }
    }
    // if we still haven't found it add the line at the end of the array
    if(!found)
        lines.add(index + ":" + x + "," + y);

    // write the array to a file
    FileUtils.writeLines(file, lines);
}

by simply doing

processFile(file, 50, 1, 1);