# parseLong(String s, int radix) - What is a radix ?

Munish Gulati

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Posts: 37

posted 12 years ago

public static long parseLong(String s, int radix) throws NumberFormatException

Examples:-

parseLong("0", 10) returns 0L

parseLong("473", 10) returns 473L

parseLong("-0", 10) returns 0L

parseLong("-FF", 16) returns -255L

parseLong("1100110", 2) returns 102L

parseLong("99", 8) throws a NumberFormatException

parseLong("Hazelnut", 10) throws a NumberFormatException

parseLong("Hazelnut", 36) returns 1356099454469L

What is a radix, and what it does in the above code examples ?

Examples:-

parseLong("0", 10) returns 0L

parseLong("473", 10) returns 473L

parseLong("-0", 10) returns 0L

parseLong("-FF", 16) returns -255L

parseLong("1100110", 2) returns 102L

parseLong("99", 8) throws a NumberFormatException

parseLong("Hazelnut", 10) throws a NumberFormatException

parseLong("Hazelnut", 36) returns 1356099454469L

What is a radix, and what it does in the above code examples ?

Munish Gulati<br />SCJP 1.4<br />Albert Einstein: There are only two ways to live your life. One is as though nothing is a miracle. The other is as though everything is a miracle.

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Dirk Schreckmann

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posted 12 years ago

JCP Help,

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Welcome to JavaRanch!

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Thanks Pardner! Hope to see you 'round the Ranch!

Dirk Schreckmann

Sheriff

Posts: 7023

posted 12 years ago

Does knowing that radix means base help to better understand these examples (which were taken from the Long class documentation)?

To review a couple of the examples briefly, parseLong("99", 8) throws a NumberFormatException because a base 8 numbering system was specified. In such a system, only 8 different digits would be used, presumably 0, 1, 2, 3, 4, 5, 6, and 7 in this case. Since 8 is not one of these digits, there is a problem with trying to turn it into a number.

You're likely used to the decimal system with its ten digits - 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. Realize that we don't have to count with ten digits, we just do, probably because we (usually) have ten digits attached to our hands.

I would guess that the example that specified a 36 digit numbering system (base 36, a.k.a. radix 36), parseLong("Hazelnut", 36), uses 0-9 as the first ten digits, representing their "normal" decimal values, with the characters of the english alphabet representing the following 26 values - ten, eleven, twelve, thirteen... So, A is ten, B is eleven, etc.

I suppose the next challenge would be to understand how to convert these different radix numbers into decimal. It's pretty darn easy.

Realize that, in decimal, two hundred and fourty-six (246) is the same as

(6 X 10^0) + (4 X 10^1) + (2 X 10^2) = 246 base 10

Notice all those tens and remember "decimal" means "base ten".

Well, to interpret (i.e. convert to decimal) a number such as 46 base 7 isn't all that different.

46 base 7 = (6 X 7^0) + (4 X 7^1) = 6 + 28 = 34 base 10

Making

To review a couple of the examples briefly, parseLong("99", 8) throws a NumberFormatException because a base 8 numbering system was specified. In such a system, only 8 different digits would be used, presumably 0, 1, 2, 3, 4, 5, 6, and 7 in this case. Since 8 is not one of these digits, there is a problem with trying to turn it into a number.

You're likely used to the decimal system with its ten digits - 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9. Realize that we don't have to count with ten digits, we just do, probably because we (usually) have ten digits attached to our hands.

I would guess that the example that specified a 36 digit numbering system (base 36, a.k.a. radix 36), parseLong("Hazelnut", 36), uses 0-9 as the first ten digits, representing their "normal" decimal values, with the characters of the english alphabet representing the following 26 values - ten, eleven, twelve, thirteen... So, A is ten, B is eleven, etc.

I suppose the next challenge would be to understand how to convert these different radix numbers into decimal. It's pretty darn easy.

Realize that, in decimal, two hundred and fourty-six (246) is the same as

(6 X 10^0) + (4 X 10^1) + (2 X 10^2) = 246 base 10

Notice all those tens and remember "decimal" means "base ten".

Well, to interpret (i.e. convert to decimal) a number such as 46 base 7 isn't all that different.

46 base 7 = (6 X 7^0) + (4 X 7^1) = 6 + 28 = 34 base 10

Making

*any*sense?
Munish Gulati

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Posts: 37