Reading text file line by line in NetBeans

Question

I'm using the following code to read from a file

int lineNumber = 0;
  try{
       BufferedReader in = new BufferedReader (new FileReader("electric.txt"));
  String line = null;
    while((line = in.readLine()) != null){
     lineNumber++;
     system.out.println("Line "+ lineNumber + " : "+ line);
     }
   } catch(IOException e){
     e.printStackTrace();
   }

My file have specific values on each line, for exemple first line is int, second string, third boolean etc...

My question is how do I get each data type in a variable?

Answer 1

Basically, in a naive approach, you just do as many reads as you need:

String firstLine = in.readLine();
String secondLine = in.readLine();
...

Then you could do something like:

Whatever dataObject = new Whatever(firstLine, secondLine, ...);

for example (maybe within a loop, as you probably want to read the data for many data objects, not just a single one).

In other words: you read the required attributes in some helper variables, to then push those into the object you want to fill with data. Advantage: this works for very large data, as you only read a few lines at a time. Downside: you have to worry about invalid files, missing lines, and such things (so you need quite a bit of error handling).

Alternatively: simply read the whole file into memory first, for example using List<String> allLines = java.util.Files.readAllLines(somePathToYourFile); Then, you iterate these allLines an further process your content, now without worrying about IOExceptions for example.

Answer 2

If you want to check whether the line is boolean, integer, or String, this is a possible solution. If you need to check that the line is long or short, double or float, etc. You still have to handle those cases.

System.out.println("Line " + lineNumber + " : " + line + ", Datatype: " + typeChecker(line));

public static String typeChecker(String line){
    if (line.equals("true")||line.equals("false"))
    return "boolean";
    else{ if (isInteger(line))
        return "int";
    }
    return "String";
}

public static boolean isInteger(String s) {
    try { 
       Integer.parseInt(s); 
    } catch(NumberFormatException e) { 
       return false; 
    } catch(NullPointerException e) {
       return false;
    }
return true;
}