Difference between Error and Exception in Java

In Java, when something goes wrong during the execution of a program, the Java Virtual Machine (JVM) throws an object that describes the problem. These problems are broadly categorized into two types:

• Errors
• Exceptions

Although both represent issues that occur during runtime, they are not the same, and it’s important to understand the differences between Errors and Exceptions for better debugging, exception handling, and application reliability.

In this article, we’ll clearly explain the difference between Errors and Exceptions in Java, with examples and a detailed comparison table.

✅ What is an Error in Java?

An Error in Java represents serious problems that a program should not try to handle. These errors are generally thrown by the JVM and indicate issues that are beyond the control of the program, such as memory leaks or stack overflow.

🔹 Technical Definition:

• Errors are instances of the class java.lang.Error.
• They are unchecked, meaning they are not checked at compile-time.
• These typically occur in the runtime environment (e.g., JVM or hardware failure).

Examples of Errors:

• StackOverflowError: Occurs when a method calls itself repeatedly without a proper stopping condition.
• OutOfMemoryError: Occurs when JVM cannot allocate memory for objects because heap space is exhausted.

public class ErrorDemo {
    public static void main(String[] args) {
        main(args); // causes StackOverflowError
    }
}

✅ What is an Exception in Java?

An Exception represents conditions that a program might want to catch and handle. These are problems that can be anticipated and recovered from during execution using proper exception handling techniques like try-catch.

🔹 Technical Definition:

• Exceptions are instances of the class java.lang.Exception.
• They include both checked and unchecked exceptions.
• Some are detected at compile-time (checked), while others happen at runtime (unchecked).

🔸 Checked Exceptions:

These are checked by the compiler. If a method can throw a checked exception, the method must either handle it using try-catch or declare it using the throws keyword.

✅ Examples:

• IOException
• SQLException

import java.io.*;

public class CheckedDemo {
    public static void main(String[] args) throws IOException {
        FileReader fr = new FileReader("file.txt"); // throws FileNotFoundException
    }
}

🔸 Unchecked Exceptions:

These are not checked by the compiler and occur at runtime. They are usually caused by programming mistakes like dividing by zero or accessing null objects.

✅ Examples:

• NullPointerException
• ArrayIndexOutOfBoundsException
• ClassCastException

public class UncheckedDemo {
    public static void main(String[] args) {
        int[] nums = new int[3];
        System.out.println(nums[5]); // throws ArrayIndexOutOfBoundsException
    }
}

Key Differences Between Error and Exception

Here’s a side-by-side comparison to help you quickly understand the distinction:

When to Use What?

🚨 Should You Catch Errors?

In general, no. Errors are meant to indicate serious problems that the application should not try to catch or handle.

For example, trying to catch an OutOfMemoryError might leave the application in an unstable state, and there may not be enough resources left to execute recovery logic.

try {
    // some code
} catch (OutOfMemoryError e) {
    System.out.println("Not recommended, app might crash anyway");
}

Use catching for exceptions only, where you can safely recover.

🧾 Summary Table

✅ Final Thoughts

Understanding the difference between Errors and Exceptions in Java is crucial for writing stable and reliable applications. Here’s the golden rule:

• Errors are serious issues related to the environment or JVM — don’t try to catch them.
• Exceptions are issues in the application code — handle them properly using try-catch or throws.

You make your Java application more robust and production-ready by handling exceptions correctly and designing your code to avoid errors like stack overflows or memory leaks.