Java Error and exception

In Java, there are two main types of problems that can occur during the execution of a program: Errors and Exceptions.

1. Errors

Errors are serious issues that occur beyond the control of the application. These are typically problems related to the Java Virtual Machine (JVM) itself, such as:

• StackOverflowError
• OutOfMemoryError
• VirtualMachineError

These errors are often unrecoverable and should not be handled in the code. When an error occurs, it’s best to let the system crash or shut down gracefully, as the environment may no longer be stable.

2. Exceptions

Exceptions are issues that arise during the normal operation of a program and can usually be anticipated and handled. For example:

• Trying to read a file that doesn’t exist.
• Invalid user input.
• Attempting to divide by zero.

Java provides a robust mechanism to handle exceptions using try-catch-finally blocks. Exceptions are further categorized into two types:

a. Checked Exceptions

These are exceptions that are checked at compile time. The compiler requires the developer to handle these exceptions explicitly, either by using a try-catch block or by declaring them in the method signature using the throws keyword.

Examples:

• IOException
• SQLException

b. Unchecked Exceptions

These are exceptions that are not checked at compile time. They usually indicate programming bugs, such as logic errors or improper use of an API. These exceptions inherit from RuntimeException.

Examples:

• NullPointerException
• ArrayIndexOutOfBoundsException
• IllegalArgumentException

Summary

Type	Checked at Compile Time	Typically Caused By	Should Be Handled?
Error	No	JVM/Internal system issues	No
Checked Exception	Yes	External issues (I/O, DB)	Yes
Unchecked Exception	No	Programming bugs	Yes (when possible)

Understanding the difference between errors and exceptions—and between checked and unchecked exceptions—helps in writing more robust and fault-tolerant Java applications.

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