CODEWITHSUNDEEP
javaarraylist
12dec1990
12dec1990

Reputation: 115

Distinguishing between the different data types in Java

I have a text file that contains the following:

Hello
1
2
3
4
5.6
LOL
23.5
34.6
23
456
Rofl.

I wrote down the code in java that would read the contents of this text file and distinguish between the 3 data types.I used try catch statements and my code works(kinda). The only problem is that it converts any whole numbers to doubles as well. For example the following is what my code is outputting:

List of integers in the textfile: [1, 2, 3, 4, 23, 456]

List of doubles in the textfile: [1.0, 2.0, 3.0, 4.0, 5.6, 23.5, 34.6, 23.0, 456.0]

List of Strings in the textfile: [Hello, 5.6, LOL, 23.5, 34.6, Rofl]

I want to prevent that from happening. Any suggestions would be appreciated.

    ArrayList<Integer> data_int=new ArrayList<Integer>();
    ArrayList<String> data_String=new ArrayList<String>();
    ArrayList<Double> data_double=new ArrayList<Double>();


    while(file.hasNext())
    {
        String s=file.next();
        System.out.println(s);

        try
        {
            Integer.parseInt(s);
            data_int.add(Integer.parseInt(s));
         }
        catch(NumberFormatException e)
        {
          data_String.add(s);
        }

        try
        {
              Double.parseDouble(s);
              data_double.add(Double.parseDouble(s)); 

        }
        catch(NumberFormatException e)
        {

        }

    }
    System.out.println("List of integers in the textfile: "+data_int);
    System.out.println("List of doubles in the textfile: "+data_double);
    System.out.println("List of Strings in the textfile: "+data_String);

Upvotes: 2

Views: 123

Answers (5)

Vivin Paliath
Vivin Paliath

Reputation: 95578

Instead of calling parseInt or parseDouble and then dealing with the exception, perhaps it would be better to use a regex with String#matches to see if the value looks like an integer or a double. Exceptions are for exceptional circumstances that happen outside normal flow; you don't want to use them to control the regular flow of your program. Since you can expect there to be non-numerical values, it is better to check the value and see what it "looks like".

To see if it is an integer, you can just use -?\\d+.

For doubles, use the regex -?\\d*\\.\\d+. This will even match strings of the form .5.

If none of these match, it is probably a string.

Upvotes: 0

Rajesh
Rajesh

Reputation: 2155

Use nested Try Catch Block:

while (file.hasNext()) {

    String s = file.next();
    System.out.println(s);

    try {
        Integer.parseInt(s);
        data_int.add(Integer.parseInt(s));
    } catch (Exception e) {

        try {
            Double.parseDouble(s);
            data_double.add(Double.parseDouble(s));
        } catch (Exception e1) {
            // TODO Auto-generated catch block
            data_String.add(s);
        }
    }

}

Upvotes: 0

ControlAltDel
ControlAltDel

Reputation: 35096

Put your double check in the catch block for the integer check

try {
  Integer.parseInt(s);
  data_int.add(Integer.parseInt(s));
} catch(NumberFormatException e) {
  try {
    Double.parseDouble(s);
    data_double.add(Double.parseDouble(s));
  } catch(NumberFormatException e) {
    data_String.add(s);
  }
}

Upvotes: 1

Amir Afghani
Amir Afghani

Reputation: 38541

Try the following with each token received:

  1. Attempt to parse the token as a int - if that passes do not attempt to parse it as an int or String.
  2. If that fails attempt to parse the token as an double. If that passes do not attempt to parse it as a String.
  3. If that fails parse the token as a String.

Remove the code where you add the data to the String datset when each prior parse attempt fails.

Upvotes: 1

dReAmEr
dReAmEr

Reputation: 7196

I think below should work for you.

while(file.hasNext()){
        String s=file.next();
        System.out.println(s);  

        try
        {
              try
               {
                Integer.parseInt(s);
                data_int.add(Integer.parseInt(s));
               }
               catch(NumberFormatException e){
                //do nothing
               }
              Double.parseDouble(s);
              data_double.add(Double.parseDouble(s)); 
        }
        catch(NumberFormatException e){
        data_String.add(s);
        }
    }

Upvotes: 0

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