Difference between error and exception in Java

In Java, there are two types of problems that can arise when executing code: errors and exceptions. Both errors and exceptions can cause your code to behave in unexpected ways, and it's important to understand the difference between the two in order to effectively handle them.

Errors in Java

Errors in Java are problems that occur at runtime and are generally considered to be unrecoverable. They are typically caused by more severe problems like hardware failures, system crashes, or out of memory errors. These types of errors cannot be handled by your code, and when they occur, your program will generally terminate abruptly. Examples of errors in Java include java.lang.StackOverflowError, java.lang.OutOfMemoryError, and java.lang.ThreadDeath.

Exceptions in Java

Exceptions in Java, on the other hand, are problems that can occur during the execution of your code, but they are generally recoverable. Exceptions are objects that represent an exceptional condition that has occurred in your program, and they can be caught and handled using try/catch blocks. Exceptions are thrown by the Java Virtual Machine (JVM) when an unexpected or exceptional event occurs. For example, if you try to open a file that doesn't exist, an IOException will be thrown.

Java provides several built-in exception classes that you can use to handle specific types of exceptions. These classes are organized in a hierarchy, with the root class being java.lang.Throwable. The two main types of exceptions in Java are checked exceptions and unchecked exceptions. Checked exceptions must be declared in the method signature, whereas unchecked exceptions do not.

Some common checked exceptions in Java include java.io.IOException, java.sql.SQLException, and java.text.ParseException. Common unchecked exceptions include java.lang.NullPointerException, java.lang.ArithmeticException, and java.lang.ArrayIndexOutOfBoundsException.

Differences between Errors and Exceptions

The main difference between errors and exceptions is that errors are generally considered to be unrecoverable, whereas exceptions are recoverable. When an error occurs, your program will typically terminate abruptly, whereas when an exception occurs, you can catch and handle it to recover from the exceptional condition.

Another difference between errors and exceptions is that errors are generally caused by more severe problems like hardware failures or out of memory errors, whereas exceptions are typically caused by problems with the application logic, such as invalid input or incorrect usage of APIs.

Errors in Java

Errors in Java are typically caused by problems with the system or environment in which the application is running. Some common types of errors include:

• Out of memory errors: These occur when the JVM runs out of memory and is unable to allocate more memory to the application.
• Stack overflow errors: These occur when the call stack becomes too deep, typically due to an infinite loop or excessive recursion.
• Thread death errors: These occur when a thread is forcibly stopped by calling the Thread.stop() method.

Errors are generally considered to be unrecoverable because they are caused by problems that are outside of the control of the application. When an error occurs, there is usually nothing that the application can do to recover from the problem, and the program will typically terminate abruptly.

Exceptions in Java

Exceptions in Java are caused by problems with the application logic, such as invalid input or incorrect usage of APIs. Exceptions are objects that represent an exceptional condition that has occurred in the application, and they can be caught and handled using try/catch blocks.

There are two types of exceptions in Java: checked exceptions and unchecked exceptions. Checked exceptions are exceptions that must be declared in the method signature, whereas unchecked exceptions do not need to be declared.

Checked exceptions are typically used for exceptional conditions that the application can reasonably be expected to handle, such as file not found errors or network connection errors. Unchecked exceptions are typically used for exceptional conditions that are not recoverable, such as null pointer exceptions or array index out of bounds exceptions.

Handling Exceptions in Java

When an exception occurs in Java, the JVM creates an exception object and throws it to the calling method. If the exception is not caught and handled by the calling method, it is passed up the call stack to the next method in the call hierarchy. This process continues until either the exception is caught and handled, or it reaches the top of the call stack and the program terminates.

To handle exceptions in Java, you can use a try/catch block. The try block contains the code that might throw an exception, and the catch block contains the code that handles the exception. If an exception occurs in the try block, the catch block is executed.

Conclusion

In conclusion, errors and exceptions are two types of problems that can occur when executing code in Java. Errors are generally considered to be unrecoverable and can cause your program to terminate abruptly, whereas exceptions are recoverable and can be caught and handled using try/catch blocks. Understanding the difference between errors and exceptions is important for effectively handling them in your code.