I want to parse multiple strings into variables from a .txt file in java. What's the easiest way to do it?

Question

What's the best way to do it? Should I use the File class and scanner? I've never done it before and can't seem to find a solid guide for it online so I figured I would ask here.

Edit:
The text file I am parsing is 3 columns, the first three are ID NAME BIRTHDATE then actual data.

Edit (code from pastie ):

public void readFromFile(File file ) 
{
    try
    {
        System.out.println("success..");
        s = new Scanner(file);
        BufferedReader input = new BufferedReader(new FileReader(file));
        String jj = null;
        while((jj = input.readLine())!=null)
        {  
            String [] words = jj.split("\\t");
            String name = "";
            String id = "";
            String birthdate ="";
            for (int i = 3; i<words.length; i+=3)
            {
                id =words[i];
                name = words[i+1];
                birthdate=words[i+2];
                Person p = new Person(id, name, birthdate);
                peopleMap.put(p.id,p);
                names.add(p);
                System.out.println("New entry added to file: "+name+"\\t"+"ID: "
                                    +id+"\\t"+"Birthdate"+birthdate);
            }
        }
    }

    catch(IOException e)
    {
    }
}

Answer 1

The easiest way depends on the format of the text file. From your other comment, it sounds like the lines are tab separated values. As a beginner you will probably find it simplest to use Scanner. Specifically, Scanner.nextLine(). Couple that with using String.split("\\t") to split the data into an array (assuming the format is tab-separated-values).

Answer 2

Simply depends on the format of the text file.

1. If its simple name value pair then you can use java.util.Properties. for example a.properties could look like:

    name=john city=san jose date=12 july 2010 

then you can load this as:

Properties props = new Properties();
props.load(new FileInputStream("a.properties"));

2. If format is different than what is supported by java.util.Properties.load() then using java.util.Scanner would be helpful to process it line by line:

    File file = new File("data.txt"); try { Scanner scanner = new Scanner(file); while (scanner.hasNextLine()) { String line = scanner.nextLine(); //Process each line seperately processLine(line); } } catch (FileNotFoundException e) { e.printStackTrace(); } 

Answer 3

If you are free to say what the syntax / structure of the text file is, then consider making it a Java properties file. Then you can load and save the file with minimal programming effort using the java.util.Properties class.

Answer 4

This is what I like to do in that situation:

Scanner s = new Scanner(file);
Scanner line;
String name;
String date;
int id;
while(s.hasNext()){
   line = new Scanner(s.nextLine());
   id = line.nextInt();
   name = line.next/*String*/();
   date = line.next/*String*/();
   /* Do something with id, name and date */
}

Maybe there is some exception handling or something like that

(Anyone want to comment on the efficiency of creating many new Scanners?)