如何从JAVA中的文件中读取这些数据

Question

I have this format of data

n
l
p1(x1) p1(x2) imp(p1)
p2(x1) p2(x2) imp(p2)
: : :
pl(x1) pl(x2) imp(pl)
r
q1(x1) q1(x2) imp(q1)
q2(x1) q2(x2) imp(q2)
: : :
qr(x1) qr(x2) imp(qr)

where n, l(number of p's) , and r(number of q's) are integers. I know how to read only integers from a file but how I can read the lines that includes strings and get the values of x1, x2, and p1 for each line?! Thanks in Advance.

Here is my code for reading integers only.

try {
            reader = new BufferedReader(new FileReader(file));
            String text = null;
            while ((text = reader.readLine()) != null) {
                // The first line gives the number of nodes (You will use to create the int[][] graph = new int[nOfNodes][nOfNodes];)
                if (c == 0) {
                    numberOfNodes = Integer.parseInt(text.trim());
                } // The second one gives the number of edges
                else if (c == 1) {
                    nOfEdges = Integer.parseInt(text.trim());
                    graph2 = new double[nOfEdges][3];
                } // And third the list of special nodes
                // `nodes` will now contains only your special constrained one
                else if (c == 2) {
                    String[] str = text.split(" ");
                    for (int i = 0; i < str.length; i++) {
                        if (str[i].trim().length() > 0) {
                            nodes.add(Integer.parseInt(str[i]));
                        }
                    }
                } else { // Then you have your edges descriptors
                    String[] str = text.split(" ");
                    for (int i = 0; i < str.length; i++) {
                        if (str[i].trim().length() > 0) {
                            graph2[c - 4][i] = Double.parseDouble(str[i]);
                        }
                    }
                }
                c++;
            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                System.out.print(e);
            }
        }

Answer 1

A quick google search led me to this tutorial on basic java I/O , and in particular, there is a section on Scanning that demonstrates how to conveniently break (aka "split" or "tokenize") your input into smaller pieces and possibly parse them in a more structured manner.

The documentation for the Scanner class has more detailed examples. I think you need something like:

String input = "p1(x1) p1(x2) imp(p1)";
Scanner s = new Scanner(input);
s.findInLine("(\\w+)\\((\\w+)\\) (\\w+)\\((\\w+)\\) imp\\((\\w+)\\)");

I haven't tested this yet, but basically "\\\\(" is for parsing a "(" and "\\\\w+" is for parsing any sequence of one or more characters. If you want to parse a sequence of digits then use "\\\\d+" instead.

Hope this helps, good luck!

Answer 2

In my opinion, the best thing for you here is using the Properties class. With the properties class you can set some properties and then read them again! This is the link which I found explains it the best!

https://www.mkyong.com/java/java-properties-file-examples/

If you don't want that, you can simply split the line to 3 strings each one containing one piece of data.

String data[] = line.split(" ");

Now find the open bracket and the close bracket and get what is between them. I added + 1 and - 1 so that it doesn't read the braces as well, only the number between.

int begin = string.indexOf('(');
int end = string.indexOf(')');
string.substring(begin + 1, end - 1);

Now just parse your string into an integer.

int number = Integer.parseInt(thedatathatyouhave);

Answer 3

Using matcher class like this

public static int numberOfPoints = -1, p=-1, q=-1;

    public static void main(String[] args) throws FileNotFoundException {

        ArrayList<Integer> dots = new ArrayList<>();
        int c = 0;
        File file = new File("D:\\ALGORTHIMS\\MASTER LEVEL\\dr. khaled\\assignment 3\\a.txt");
        BufferedReader reader = null;


        try {
            reader = new BufferedReader(new FileReader(file));
            String text = null;
            while ((text = reader.readLine()) != null) {

                try {
                    if(c==0)
                    { numberOfPoints=Integer.parseInt(text); c=1;}
                    if(c==1)
                    { p=Integer.parseInt(text);c=2;}
                    if(c==2)
                        q=Integer.parseInt(text);

                } catch (NumberFormatException e) {

                    Matcher m = Pattern.compile("\\(([^)]+)\\)").matcher(text);
        while (m.find()) {

           dots.add(Integer.parseInt(m.group(1)));
        }

                }

            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (reader != null) {
                    reader.close();
                }
            } catch (IOException e) {
                System.out.print(e);
            }
        }