finally clause

Quote:

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You can do anything inside a finally clause that you can do elsewhere, including executing break, continue, or return statements, or throwing exceptions. Such actions inside a finally clause, however, can have some surprising effects. For example, consider a finally clause that is entered because of an uncaught exception. If the finally clause executes a return, the method would complete normally via the return, not abruptly by throwing the exception. The exception would have in effect been handled by the finally clause instead of a catch clause.
From: Exceptions in Java

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Hello
What does this text want to tell?
Please example.
With thanks

Quote:

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Originally Posted by arefeh

Hello
What does this text want to tell?
Please example.
With thanks

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If a finally clause returns, no exception (that wasn't handled) will be thrown; e.g.

Code:

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void noException() {
  int[] a= null;
  try {
      a[42]= 54; // this throws an Exception
  }
  finally {
      return; // but it's muffled away here
  }
}

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kind regards,

Jos

I run following program and got this error:
Exception in thread “main” java.lang.NullPointerException:
At Test1.noException(Test1.java:8)
At Test1.main(Test1.java:17)

Code:

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class Test1
{
        void noException()
        {
                int[] a= null;
    try
    {
            a[42]= 54; // this throws an Exception
    }
    finally
    {
            [b]//return; // but it's muffled away here[/b]
    }
}
  public static void main(String[] args)
  {
          new Test1().noException();
  }
}

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But I did not get above error with return in finally clause.
It is very wonderful! Thank you.


My new question:
I am sorry. I do not know what the example can I write with this quote? Please guide me.

Quote:

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consider a finally clause that is entered because a return true; statement was executed inside the try block. If the finally clause executes a return false; statement, the method will return false.

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Quote:

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Originally Posted by arefeh

My new question:
I am sorry. I do not know what the example can I write with this quote? Please guide me.

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A finally clause is always executed last, just before any optional return statement in a try block, e.g.

Code:

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boolean returnTrue() {
  try {
      return 1 > 0; // this is supposed to return true
  }
  finally {
      return false; // but false is returned instead
  }
}

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kind regards,

Jos

How wonderful!
This method returns false and I saw this result.


New question:
We know that with existing return in a method or in a constructor, we will exit from this method or this constructor.
For example:
void a()
{
System.out.println("This is a method");
return;
}

Then, why with existing return in r_eturn method, we can not exit from r_eturn method?

Code:

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  void r_eturn()
  {
          try
          {
                  return;
          }
          finally
          {
                  System.out.println("OK");
          }
  }

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it seemes that return statment cause we exit from a block.
this block can be a method, an if, an else, a try or finally.
OK?

Oh!I was not true.
I run following program and I saw that control exit from the method.

Code:

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  void r_eturn()
  {
          if(1>0)
          {
                  System.out.println("True");
                  [b]return;[/b]
          }
          System.out.println("This is a method");
  }

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Then, finally clause must run.