How to Resolve the "Unhandled exception type IOException" Error in Java?

What causes the "Unhandled exception type IOException" error in my Java code?

import java.io.*;

class IO {
    public static void main(String[] args) { 
       BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));    
       String userInput;  
       while ((userInput = stdIn.readLine()) != null) {
          System.out.println(userInput);
       }
    }
}

The 'Unhandled exception type IOException' error in Java occurs when a method that can throw a checked exception (like IOException) is called without proper exception handling. In Java, certain exceptions must be either caught using a try-catch block or declared in the method's signature using a throws clause.

import java.io.*;

class IO {
    public static void main(String[] args) { 
       BufferedReader stdIn = new BufferedReader(new InputStreamReader(System.in));   
       String userInput;  
       try {
           while ((userInput = stdIn.readLine()) != null) {
               System.out.println(userInput);
           }
       } catch (IOException e) {
           e.printStackTrace(); // Handle exception here
       }
    }
}

Causes

• The method readLine() from BufferedReader is a checked exception, which means it must be handled either by a try-catch block or declared in the main method's signature.
• The code provided attempts to call readLine() without specifying how to handle IOException.

Solutions

• Wrap the readLine() call in a try-catch block to catch the IOException.
• Declare the main method with a throws clause to indicate that it can throw IOException.

Mistake: Not using a try-catch block when calling readLine() which can throw an IOException.

Solution: Wrap the readLine() call in a try-catch block to properly handle the exception.

Mistake: Neglecting to declare IOException in the method signature.

Solution: Use 'public static void main(String[] args) throws IOException' to propagate the exception.