Java Exception

General info

• The mild error conditions that your program may encounter.
• Exception categories.
• Common Exceptions.
• Use try, catch, and finally statements.
• Create your own exception.
• Develop programs to handle your own exceptions.

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Exception catergories

• Throwable-->Exception for mild error, coverable, like IOException, NullPointerException
• Throwable -->Error for serious error condition, uncoverable, like AWTError,OutOfMemoryError
• Exception:
  • Checked exception: must catch
  • Unchecked exception: option for catch, like runtime exception

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Common Exceptions

Exception may occur on the conditions:

• The file you try to open does not exist
• The network connection is disrupted
• Operands being manipulated are out of prescribed ranges
• The class file you are interested in loading is missing
• An error class defines serious error conditions

Common Exceptions

• ArithmeticException
• NullPointerException
• NegativeArraySizeException
• ArrayIndexOutOfBoundsException
• SecurityException

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Use try/catch/finally

• throws Exception in the method declaration
• try/catch -- one or multiple exceptions
• try/finally
• try/catch/finally
• definately access block -- finally

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Create your own exception

• extends Exception
• one construtor should have a String as parameter to describe reason.
• call super(reason) in one of constructors.
• handle your own exception

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Develop programs to handle your own exceptions

• Enter some wrong data throw WrongInputException.
• Calculate result not satisfied, NotSatisfiedException.
• Limited work time, OverTimeException.
• etc.

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