Error vs Exception in Java: Key Differences and Examples

When writing Java programs, you often face issues called errors and exceptions. These are unexpected events that disrupt the normal flow of your application. Understanding these problems is crucial because it helps you build stable and reliable software.

In Java, both erros and exceptions belong to a common superclass called Throwable. This means they can be thrown and caught in the program but have different roles and behaviors.

This blog will explain the key differences between errors and exceptions, their common types, examples, and how to handle them effectively. Learning these concepts allows you to write better Java code to manage problems smoothly.

Taking software engineering courses can make understanding such topics easier and improve your programming skills.

Must read: Difference Between Throw and Throws in Java: Complete Guide with Examples

Error vs Exception in Java – Key Differences

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What are Errors in Java?

Errors in Java are serious problems arising from system failures or resource limitations. Programs are not meant to handle them, as they indicate issues outside the application’s control. Errors are unchecked and part of the Java.lang.Error class.

Common Error Examples

• OutOfMemoryError: JVM runs out of memory.
• StackOverflowError: Too many method calls.
• NoClassDefFoundError: Required class not found at runtime.

public class Main {
    public static void recursiveCall() {
        recursiveCall(); // infinite recursion
    }

    public static void main(String[] args) {
        recursiveCall();
    }
}

Output:

Exception in thread "main" java.lang.StackOverflowError

Explanation: This code causes infinite recursion, resulting in a StackOverflowError. Errors like this can’t be caught easily.

Also read: Recursion in Java: A Comprehensive Guide

What are Exceptions in Java?

Exceptions represent conditions that the program can handle. They occur due to logical or user-related issues during runtime. Java allows you to catch and handle these exceptions using try-catch blocks.

Common Exception Examples

• NullPointerException: Accessing a null reference.
• IllegalArgumentException: Invalid arguments passed.
• IOException: File or network issues.

Exception Example in Java

public class Main {
    public static void main(String[] args) {
        try {
            String s = null;
            System.out.println(s.length());
        } catch (NullPointerException e) {
            System.out.println("Caught NullPointerException");
        }
    }
}

Output:

Caught NullPointerException

Explanation: The program handles the exception using a try-catch block. It prevents the program from crashing.

Check out: Comprehensive Guide to Exception Handling in Java

Types of Exceptions in Java

Exceptions are divided into two main categories: Checked and Unchecked.

Checked Exceptions

These are checked at compile-time. You must handle them using try-catch or declare them using throws.

import java.io.*;

public class Main {
    public static void main(String[] args) {
        try {
            FileReader fr = new FileReader("file.txt");
        } catch (IOException e) {
            System.out.println("File not found");
        }
    }
}

Output:

File not found

Explanation: IOException is a checked exception, and the compiler forces you to handle it.

Must read: Control Statements in Java: What Do You Need to Know in 2025

Unchecked Exceptions

These occur at runtime and are not checked during compilation.

public class Main {
    public static void main(String[] args) {
        int[] arr = new int[3];
        System.out.println(arr[5]);
    }
}

Output:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException

Explanation: Unchecked exceptions like this don’t require explicit handling during compilation.

Also read: Array in Java: Types, Operations, Pros & Cons

When to Use Exceptions and When Not To

Understanding when to use exceptions is crucial for writing clean and effective Java code.

Use Exceptions:

• When the error is recoverable (e.g., file not found, wrong user input).
• To signal conditions that a caller can catch and handle.

Avoid Using Exceptions:

• For flow control or minor issues.
• For programming errors (e.g., null checks can be avoided with validations).

Best Practices for Error and Exception Handling

Effective error handling leads to more robust and maintainable code. Follow these best practices:

• Catch specific exceptions instead of generic Exception
• Use finally blocks for cleanup
• Avoid swallowing exceptions without logging
• Document the exceptions a method can throw using @throws
• Don’t handle Error unless absolutely necessary

Conclusion

In Java, both errors and exceptions are subclasses of Throwable, but they serve different purposes. Errors indicate serious problems that are beyond the control of the application, such as system crashes or resource exhaustion. These are usually not handled in the code. On the other hand, exceptions represent issues that a program can anticipate and handle, like invalid input or missing files.

You can write more stable and maintainable Java applications by understanding their differences, types, and real-world use cases. Focus on catching exceptions where necessary, avoid overusing try-catch blocks, and never try to handle system-level errors unless required.

Proper error and exception handling is key to building reliable Java software.

FAQs

1. What is Throwable in Java and how is it related to Error and Exception?

In Java, Throwable is the superclass of all errors and exceptions. Both Error and Exception are its direct subclasses. Anything that can be thrown using the throw keyword must be a subclass of Throwable.

2. Why are Errors not recommended to be caught in Java?

Errors indicate critical failures like memory leaks or JVM crashes. These are not meant to be recovered from within code. Catching them may hide serious issues and lead to unstable behavior, so it's generally discouraged.

3. What is the role of try-catch in Exception handling?

The try-catch block allows developers to catch runtime exceptions and prevent program crashes. It wraps risky code in a try block and handles possible exceptions in the catch block, ensuring smoother execution.

4. What is the difference between checked and unchecked exceptions?

Checked exceptions are checked at compile-time and must be handled explicitly using try-catch or throws. Unchecked exceptions occur at runtime and don’t require mandatory handling, though it’s good practice to handle them where needed.

5. Can we create custom exceptions in Java?

Yes, Java allows creating custom exceptions by extending the Exception class (for checked) or RuntimeException (for unchecked). Custom exceptions improve readability and allow developers to handle domain-specific errors.

6. What happens if an exception is not handled in Java?

If an exception is not caught or declared using throws, the JVM will terminate the program and print a stack trace. This abrupt termination may lead to data loss or corrupted state.

7. Are runtime exceptions the same as errors in Java?

No. Runtime exceptions are a type of Exception and represent programming mistakes, like null references. Errors are more severe, arise from JVM or hardware issues, and usually cannot or should not be handled.

8. How does exception propagation work in Java?

If a method throws an exception and doesn’t handle it, it is propagated up the call stack. The calling method must either handle it or declare it using throws. Propagation continues until the exception is handled or the JVM halts.

9. What is the finally block and when is it used?

The finally block is used to execute code after the try-catch block, regardless of whether an exception occurred. It's commonly used for cleanup actions like closing files or releasing resources.

10. Can we catch multiple exceptions in a single catch block?

Yes. From Java 7 onwards, you can catch multiple exceptions in a single catch block using the pipe (|) symbol. This helps avoid repetitive code when multiple exceptions share the same handling logic.

11. Is it possible to throw an error explicitly in Java?

Yes, it is possible to throw an error using the throw keyword, but it’s rarely done. Since errors represent critical failures, throwing them manually is discouraged and should only be done for very specific low-level cases.

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