WAP that initialize an integer and display whether it is single digit two digit three digit or more than three digits?

Answer 1

Please note that the answer below is the most expandable answer. By this I mean that it can be easily changed to display the output given for any number of digits in a number. There are far simpler solutions which do not require any explanation, but are useless in an evolving setting.

To answer this question, we need to look at the Math.log10 function. Ignoring the possible anomalous results of this function (check the current Java API to find out what other results are possible), we can find the number of digits in a number by using: (log10(n) + 1). If n is equal to the value 10^m for a value m, then the function will return m. That is to say, if n is equal to 10, then the result of the function will be 1, since 10^1 = 10. Likewise, if n is equal to 100, then the result of the function will be 2, since 10^2 = 100, and so forth. If you look at the numbers in between, you will find the function returns a decimal result. log10(99) = 1.9956, for example. This means that the range of answers you will get for the values [10,99] will return the range of answers from [1.0,2.0). The same can be found looking at the range of values [100,999] which return in the range [2.0,3.0). From this we find that the function log10 always returns either an integer or a fractional value which will always be at most 1.0 less than the number of digits in the number sent to it. In either case, if we simply truncate it (cast the double as an int) and add 1, we come up with our getNumDigits function.

int getNumDigits(int n) {

return ((int) Math.log10(n)) + 1;

}

And to finish up your question, we can add in another method to deal with the results.

// we're assuming the number n comes from somewhere else,

// whether hard-coded or passed as input to the program

void displayNumDigits(int n) {

switch(getNumDigits(n)) {

case 1:

System.out.println("One digit");

break;

case 2:

System.out.println("Two digits");

break;

case 3:

System.out.println("Three digits");

break;

default:

System.out.println("More than three digits");

}

}

Answer 2

The core of it:

for (ndig=1; (n/=10)!=0; ++ndig);