Exceptions and Errors in Java

In this article, we are going to discuss exceptions and errors Java.

Exception

Exception are something that disrupts the normal flow of application. Once an exception is occurred, the statement after that are not executed.

Types of Exception

Exception can happen in both compile time and run time. There are 2 types of Exception in Java.

• Checked Exception
  These exceptions arise during compilation, thus handling them there is necessary. Exceptions that are children of the Exception class and do not extend the RuntimeException class are known as checked exceptions.
  Whenever we are reading a file in our java application, we need to handle FileNotFoundException to handle cases where files are not found. Compiler force us to handle such checked Exceptions.

Figure 1: IDE suggesting to handle CheckedException

Examples of Checked Exceptions are:- SQLException, IOException, etc

• Unchecked Exception
  These types of exception are occurred in Runtime. RuntimeException and its sub classes are unchecked exceptions. Runtime Exceptions are not required to be handled at compile time.
  Examples of Unchecked Exceptions are:- NullPointerException, ArrayIndexOutOfBoundsException, ArithmeticException, NumberFormatException, etc.

Exception Hierarchy

Figure 2 : Exception Hierarchy in Java

Throwable class is the parent class of all exceptions. Subclasses of the Throwable class include the Exception and Error classes. Then, exception is divided into Checked and Unchecked Exception categories. When handling exceptions in Java, we can utilize throws and try-catch blocks.

Errors

Errors are occurred in Runtime. They normally occurs due to lack of system resources or fault in environment they are running. Error is thrown by JVM in a scenario which is fatal and there is no way for the application program to recover from that error.
Since Error is sub class of Throwable, we can catch Throwable but it is not advised to catch error since error are serious issue in the system, instead we need to understand the error and fix the code.

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Examples of Errors are: StackOverFlowError, OutOfMemoryError, etc.

Conclusion

Exception and Errors both are sub class of Throwable class. Exception can occur in both compile time and runtime whereas errors mostly occur in runtime. We can use exception handling mechanism to handle exceptions whereas Error are not suggested to be handled.

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