Pre-requisite :  Java : Scanner : User input, Parsing and File Reading
Below scanner file reading example throwing “java.util.InputMismatchException” because using scanner.next(regex) but some words in test data  not matching regex “\W” for word as in “Sr. project Lead” in given example.

Test data in file

Saurabh Gupta 36 "Sr project Lead" Noida
Sailesh
Nagar 34 "Project Lead"

Example

package scanner;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class ScannerToReadInputFromFile {
	public static void main(String[] args) {
	try {
		// Decalare Scanner and intialize with File input object
		Scanner sc = new Scanner(
		new File("C:\\Users\\Saurabh Gupta\\Desktop\\Data.txt"));
		while (sc.hasNextLine()) {
		   //System.out.println(sc.next(Pattern.compile("\\w+")));
			}
		} catch (FileNotFoundException ex) {
		    ex.printStackTrace();
		}
	}
}

Output

Saurabh
Gupta
36
Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:864)
    at java.util.Scanner.next(Scanner.java:1485)
    at scanner.ScannerToReadInputFromFile.main(ScannerToReadInputFromFile.java:17)


Solution

Always handle exception while using regular expressions. In this example pattern is not matching for ‘Sr Project Lead’ because word pattern allow on [A-Za-z0-1] char only.
		

		
		
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