Error Handling Java
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Error Handling Java Best Practices
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Java Error Handling Design Pattern
Computer Glossary Who is Who Java - Exceptions Advertisements Previous Page Next Page An exception (or exceptional event) is a problem that arises during the execution of a program. When an Exception occurs the normal flow of the program is disrupted and the program/Application terminates abnormally, which is not recommended, therefore, these exceptions are to be handled. An exception can occur for many different reasons. Following are some scenarios where an exception occurs. A user has entered an invalid data. A file that needs to be opened cannot be found. A network connection has been lost in the middle of communications or the JVM has run out of memory. Some of these exceptions are caused by user error, others by programmer error, and others by physical resources that have failed in some manner. Based on these, we have three categories of Exceptions. You need to understand them to know how exception handling works in Java. Checked exceptions − A checked exception is an exception that occurs at the compile time, these are also called as compile time exceptions. These exceptions cannot simply be ignored at the time of compilation, the program
Catching and Handling Exceptions The try Block The catch Blocks The finally Block The try-with-resources Statement Putting It All Together Specifying the Exceptions Thrown by java catch exception a Method How to Throw Exceptions Chained Exceptions Creating Exception Classes Unchecked try catch throw java Exceptions The Controversy Advantages of Exceptions Summary Questions and Exercises Trail: Essential Classes Home Page > Essential
Exception E Java
Classes «Previous•Trail•Next» Lesson: Exceptions The Java programming language uses exceptions to handle errors and other exceptional events. This lesson describes when and how to use exceptions. What Is an Exception? http://www.tutorialspoint.com/java/java_exceptions.htm An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions. The Catch or Specify Requirement This section covers how to catch and handle exceptions. The discussion includes the try, catch, and finally blocks, as well as chained exceptions and logging. How to Throw Exceptions This section covers the throw statement https://docs.oracle.com/javase/tutorial/essential/exceptions/ and the Throwable class and its subclasses. The try-with-resources Statement This section describes the try-with-resources statement, which is a try statement that declares one or more resources. A resource is as an object that must be closed after the program is finished with it. The try-with-resources statement ensures that each resource is closed at the end of the statement. Unchecked Exceptions The Controversy This section explains the correct and incorrect use of the unchecked exceptions indicated by subclasses of RuntimeException. Advantages of Exceptions The use of exceptions to manage errors has some advantages over traditional error-management techniques. You'll learn more in this section. Summary Questions and Exercises
« Previous • Trail • Next » Your use of this page and all the material on pages under "The Java Tutorials" banner is subject to these legal notices. Copyright © 1995, 2015 Oracle and/or its affiliates. All rights reserved. Problems with the examples? Try Compiling and Running the Examples: FAQs. Complaints? Compliments? Suggestions? Give us your feedback. Previous page: Table of Contents Next page: What Is an Exception?Filed Under: Exception HandlingIn this tutorial we will discuss what is an exception and how it can be handled in java programming language. What is an exception? An Exception can be anything which interrupts the normal flow http://beginnersbook.com/2013/04/java-exception-handling/ of the program. When an exception occurs program processing gets terminated and doesn't continue further. In such cases we get a system generated error message. The good thing about exceptions is that they can be handled. We will cover the handling part later in this same tutorial. When an exception can occur? Exception can occur at runtime (known as runtime exceptions) as well as at compile-time (known Compile-time exceptions). Reasons for Exceptions There error handling can be several reasons for an exception. For example, following situations can cause an exception - Opening a non-existing file, Network connection problem, Operands being manipulated are out of prescribed ranges, class file missing which was supposed to be loaded and so on. Difference between error and exception Errors indicate serious problems and abnormal conditions that most applications should not try to handle. Error defines problems that are not expected to be caught under normal java error handling circumstances by our program. For example memory error, hardware error, JVM error etc. Exceptions are conditions within the code. A developer can handle such conditions and take necessary corrective actions. Few examples - DivideByZero exception NullPointerException ArithmeticException ArrayIndexOutOfBoundsException Advantages of Exception Handling Exception handling allows us to control the normal flow of the program by using exception handling in program. It throws an exception whenever a calling method encounters an error providing that the calling method takes care of that error. It also gives us the scope of organizing and differentiating between different error types using a separate block of codes. This is done with the help of try-catch blocks. Why to handle exception? If an exception is raised, which has not been handled by programmer then program execution can get terminated and system prints a non user friendly error message. Ex:-Take a look at the below system generated exception An exception generated by the system is given below Exception in thread "main" java.lang.ArithmeticException: / by zero at ExceptionDemo.main(ExceptionDemo.java:5) ExceptionDemo : The class name main : The method name ExceptionDemo.java : The filename java:5 : Line number For a novice user the above message won't be easy to understand. In order to let them know that what went wrong we use exception handling in java program. We handle such co