CODEWITHSUNDEEP
javajava.util.scanner
Peter S
Peter S

Reputation: 575

Java Scanner hasNext() skips empty lines

The log file I want to work with is tab-separated and looks like this:

2019-06-06 10:01:02     1.0
2019-06-06 10:25:12 100.0
2019-06-06 11:02:32     2.0

I use the following code to scan through the file:

import java.util.*;
import java.io.*;

public class FirstTry {
    public static void main(String[] args) 
    {
        String fileName = "LogFile.csv";
        File file = new File(fileName);
        try
        {
            Scanner inputStream = new Scanner(file);
            while (inputStream.hasNext()){
                String data = inputStream.nextLine();
                String[] values = data.split("\\t");
                System.out.println(values[0] + "    " + values[1]);
            }
            inputStream.close();
        }
        catch (FileNotFoundException e) {
            e.printStackTrace();
        }
    }
}

The line

System.out.println(values[0] + "    " + values[1]);

prints the following, working output:

2019-06-06 10:01:02    
2019-06-06 10:25:12    100.0
2019-06-06 11:02:32

but 

System.out.println(values[0] + "    " + values[2]);

prints:

2019-06-06 10:01:02    1.0
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException

Why is this exceptions raised vor values[2] and not values [1]?

Edit: Sublime Text Screenshot of the LogFile with the Tabs (5 in total) marked: enter image description here

Edit 2:

String[] values = data.split("\\t+");
System.out.println(values[0] + "    " + values[1]);

prints:

2019-06-06 10:01:02    1.0
2019-06-06 10:25:12    100.0
2019-06-06 11:02:32    2.0

System.out.println(values[0] + " " + values[2]);results in an java.lang.ArrayIndexOutOfBoundsException

Upvotes: 0

Views: 206

Answers (2)

Zain Arshad
Zain Arshad

Reputation: 1907

The problem as stated by other is that there are empty entries in the array i.e.

["2019-06-06 10:01:02", "", "1.0"]

So you need to delete all such entries. Using Java 8 this can be done like:

// You have the "values" array now do this...
String[] correctValues = Arrays.stream(values)
            .filter(value ->
                    value != null && value.length() > 0
            )
            .toArray(size -> new String[size]);
// Rest of the code ...

Upvotes: 0

IQbrod
IQbrod

Reputation: 2265

Result of String[] values = data.split("\\t");

1: ["2019-06-06 10:01:02", "", "1.0"]
2: ["2019-06-06 10:25:12", "100.0"]
3: ["2019-06-06 11:02:32 ", "", "2.0"]

Note that double tabulation will split to an empty String. On line 2 there is a single tabulation which results in an ArrayOutOfBoundsException because values does not have a third value.

As mentionned by @Thilo, a split on "\\t+" should fix your problem

Upvotes: 2

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