Simple principle and application of exception handling mechanism in Java

Exceptions are abnormal conditions or errors that occur when a Java program is run (not compiled), similar to real-life events, where real-life events can contain information about the time, place, people, and plot of an event, which can be represented by an object, and Java uses an object-oriented approach to handling exceptions. It encapsulates each exception that occurs in the program into an object that contains information about the exception.

Java classifies exceptions, and different types of exceptions are represented by different Java classes. The root class for all exceptions is java.lang.throwable,throwable and derives two sub-classes: Error and Exception,error represent a serious problem that the application itself cannot overcome and recover, and the program is only dead, for example, system problems such as memory overflow and thread deadlock. Exception said that the program can also overcome and restore the problem, which is divided into system anomalies and common anomalies, system anomalies are the defects of the software itself caused by problems, that is, the software developers to consider the problem caused by poor, software users can not overcome and restore this problem, In this case, however, the software system can continue to run or let the software die, for example, array scripting out of bounds (arrayindexoutofboundsexception), null pointer exception (NULLPOINTEREXCEPTION), Class Conversion Exception (classcastexception), common exception is the operation of the environment changes or anomalies caused by the problem, is the user can overcome the problem, for example, network disconnection, hard disk space is not enough, after such an exception, the program should not die.

Java provides a different solution for system exceptions and common exceptions, and the compiler enforces common exceptions that must try: Catch processing or using the throws declaration continues to be thrown to the upper call method processing, so the common exception is also called the checked exception, and the system exception can be handled or not handled, so the compiler does not enforce with try. catch processing or declaration with throws, so system exceptions are also known as unchecked exceptions.

Simple principle and application of exception handling mechanism in Java