[JAVA]I need help with indexOf() and substring()

I have to make a program that calculates the volume of a circle and then tells me the number of numbers to the left and right of the decimal. I was told to use indexOf and substring to do this. (i.e 23.456 - 2 numbers to the left and 3 to the right). How would i go about doing this? I cannot find a tutorial to show me how to use it in this way.

Thanks,
Andy

You should convert the float to a string

Code:

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String num = (String)myfloat;

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Then, use indexOf() to find the position of the decimal point, which is one less than the length of the string before that point so

Code:

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int placesBefore = num.indexOf((int)('.')) + 1;

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and then take that away from the length of the string to obtain the number of characters after the point

Code:

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int placesAfter = num.length() - placesBefore;

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I got it workin tho not exactly the way you did it. Can u explain to me what indexOf does and why i might of needed substring?

I've have no idea why I put the +1 in there, sorry about that one. It should actually look like

Code:

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String num = (new Float(myfloat)).toString();
int placesBefore = num.indexOf((int)'.'),
  placesAfter = num.length() - placesBefore - 1;

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[edit]

'Can u explain to me what indexOf does' - Read API (http://java.sun.com/j2se/1.4.2/docs/...ng/String.html) tut for java.lang.String
'and why i might of needed substring?' - I'm not entirely sure, but I think that you were expected to do

Code:

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String beforeDecimal = substring(0, placesBefore);
int afterDecimal = substring(placesBefore + 1);
int placesAfter = afterDecimal.length();

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or you could do

Code:

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String[] decimalSides = num.split("\.");
int beforeDecimal = decimalSides[0],
  afterDecimal = decimalSides[1];

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which would be probably better.

Ok thanks you were kinda of right about the -1. I had to use it on the after.length() - before - 1 because it it counting the decimal and i dont need it to count that lol

I suppose I should test my stuff I post before posting :tongue:

I think i got it now thanks for this.

Code:

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class Andy
{

  void Andy()
  {
  }
 
  Andy()
  {
  }
}

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I know Andy() is a constructor, but the class Andy is not right?

Yeah, the second Andy() is a constructor, but the class isn't a constructor. A constructor is a method that sets up an instance of its class to be ready for use.

SO it has 2 constructors right?
I read somethign about what the void meant and didnt really understand it, can you try and explain it to me?

Quote:

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Originally Posted by Andy88

SO it has 2 constructors right?

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No, only one constructor. The other method has a return type, so it's just a standard instance method.

Quote:

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Originally Posted by Andy88

I read somethign about what the void meant and didnt really understand it, can you try and explain it to me?

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It's the return type declared when a method doesn't return a value.