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# how to convert string to int

Greenhorn
Posts: 12
how to convert string to int without using any standard function in java.
write an algorithm that implements parseInt?

Ranch Hand
Posts: 1296
Depends on what you mean by standard functions. Off the top of my head you could take a String, examine it to be sure that is contains all digits (simple if you use a regular expression, but is that allowed?), reverse the String, examine each digit, convert it to an int (or Integer) using some sort of mapping, multipliy it by the appropriate power of 10, and add the result to the total. Sounds pretty easy, but I'd rather use Integer.parseInt().

author and iconoclast
Sheriff
Posts: 24220
40

how to convert string to int without using any standard function in java.
write an algorithm that implements parseInt?

This is very clearly a homework or interview question, as are all the other questions you've posted this morning. Folks, please don't provide a direct answer.

The way things work around here is you show us how far you've gotten, and we give you hints to help when you're stuck.

Ranch Hand
Posts: 961
Well, supposing your number is stored in a String object, like this:

String number = "123456";

Then you could say that "123456" is the same as:

6 x 1 = 6
5 x 10 = 50
4 x 100 = 400
3 x 1000 = 3000
2 x 10000 = 20000
1 x 100000 = 100000

Total = 123456

Right?

Well, now give it a look at the java.lang.Character documentation and read about the digit(char ch, int radix) method.

Good luck!