Compile Error: Unhandled Exception

Why This Happens

Java's checked exception system requires that checked exceptions (everything except RuntimeException and Error subclasses) are either caught with try-catch or declared in the method's throws clause. This is a compile-time enforcement of exception handling.

The Problem

public void readFile() {
    FileReader reader = new FileReader("data.txt"); // Throws IOException - not handled
}

The Fix

// Option 1: Catch the exception
public void readFile() {
    try {
        FileReader reader = new FileReader("data.txt");
    } catch (IOException e) {
        System.err.println("Cannot read file: " + e.getMessage());
    }
}

// Option 2: Declare in throws clause
public void readFile() throws IOException {
    FileReader reader = new FileReader("data.txt");
}

Step-by-Step Fix

1. 1

   Identify the checked exception

   Read the error message for the exception type that must be handled.

2. 2

   Decide handling strategy

   Choose between catching the exception (if you can handle it) or declaring it in the throws clause (if the caller should handle it).

3. 3

   Add try-catch or throws

   Wrap the call in try-catch for local handling, or add throws to the method signature to propagate it.