detect numeric value w/o regular expression

[usgog]

I have a string input, which might be a numeric value. So I want to
return false if it is a numeric value. What is the best and simplest
way to do that without using regular expression or import other
libraries? Because I don't want to load all the references. So
something like charAt and foreach to detect a char in the string?

 

[hiwa]

I have a string input, which might be a numeric value. So I want to
return false if it is a numeric value. What is the best and simplest
way to do that without using regular expression or import other
libraries? Because I don't want to load all the references. So
something like charAt and foreach to detect a char in the string?

You could use Character.isDigit() method if the string consists of
0-9 only.

 

[Luc The Perverse]

I have a string input, which might be a numeric value. So I want to
return false if it is a numeric value. What is the best and simplest
way to do that without using regular expression or import other
libraries? Because I don't want to load all the references. So
something like charAt and foreach to detect a char in the string?

You are not adding to the bulk of your program by using imported libraries.

Regardless

boolean isNumeric(String x){
for(char c : x.toCharArray())
if(c<'0||c>'9')
return false;
return true;
}

If you need it to work with negatives or decimal points it will require a
little extra work - not too much.

 

[Andrew Thompson]

I have a string input, which might be a numeric value. So I want to
return false if it is a numeric value. What is the best and simplest
way to do that without using regular expression or import other
libraries? Because I don't want to load all the references.

I don't think it will take long, for java.lang
classes (though any try/catch could add a
wallop of processing time).

<sscce>
class TestNumeric {
public static void main(String[] args) {
String input = "1.23";
Float f = new Float(input);
System.out.println(f);

input = "1.23f";
f = new Float(input);
System.out.println(f);

input = "1.23e7";
f = new Float(input);
System.out.println(f);

input = "f1.23";
f = new Float(input);
System.out.println(f);
}
}
</sscce>

<output>
1.23
1.23
1.23E7
Exception in thread "main" java.lang.NumberFormatException:
For input string: "f1.23"
....
</output>

Andrew T.