Chapter 7: Java Exception Handling

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Chapter 7 Java Exception Handling
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Basics of Exceptions

• An Exception usually signals an error in your
  program.
• You need to handle exception only is unusual or
  catastrophic situations
• Commonly happened situations like input errors
  should be handled by your code
• Most of the exception classes inherit from the
  Java class Exception
• If a method has the potential of generating an
  exception you must either
• Deal with it in your code, or
• Register that you method may throw that exception

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Basics of Exceptions (cont)

• Subclasses of RunTimeException, a subclass of
  Exception, are exempted from the previous
  requirement
• Ex ArithmeticException, ClassCastException, ..
• Specifying a throwable exception
• Double myMethod throws IOExecption
• Dealing with exception in your code (Try-catch
  block)
• Try
• you code
• catch ( Exception e )
• Ex TestTryCatch, TestLoopTryCatch,
  TestLoopTryCatch2
• You can have more than one catch block
• In addition, you can use a finally block at the
  end of all catch blocks. This will be always
  executed
• Ex TryBlockTest.java

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Basics of Exceptions (cont)

• You can use two method from the Throwable class,
  the parent of Eception, getMessage() and
  printStackTrace()
• Ex (2) TryBlockTest.java
• You can define your own exception class which
  should (in almost all cases) inherit from
  Exception or one of its children. Ex
  DreadfulProblemException.java
• You can throw the exception after catching it
• Example of a define one define your own