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 cant seem to find a solid guide for it online so I figured I would ask here.

Thanks!

Answer 1

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 2

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 3

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"));

1. 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 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?)