Java Regex for positive numbers only excluding zero

Question

I am struggling with java regex. I want to validate if a number is greater than zero and it should not be negative also

0.00011 - GOOD
1.222 - GOOD
0.000 - BAD
-1.1222 - BAD

So anything above zero is okay. Is this possible in java regex?

Answer 1

Don't do this with regexes. Do this with BigDecimal :

// True if and only if number is strictly positive
new BigDecimal(inputString).signum() == 1

Answer 2

Why regex?

You can simply do something like following

 double num=0.00011;
    if(num>0){
        System.out.println("GOOD");
    }else{
        System.out.println("BAD");
    }

Or if you rally want to do this in hard way you can try some thing as follows too

 String num="-0.0001";
   char sign=num.split("\\.")[0].charAt(0);
   if(sign=='-' || Double.parseDouble(num)==0.0){
       System.out.println("BAD");
   }else {
       System.out.println("GOOD");
   }

Answer 3

It is better not to solve it using regex, still here is one of the solution how to solve it using regex:

 public static void main (String[] args) throws java.lang.Exception
  {
    String str = "0.0000";

    Pattern p = Pattern.compile("(^-[0-9]+.+[0-9]*)|(^[0]+.+[0]+$)");
    Matcher m = p.matcher(str);
    if (m.find()) {
      System.out.println("False");
    }else{
      System.out.println("True");
    }
  }

Here is the demo

Answer 4

Try

^(0\\.\\d*[1-9]\\d*)|([1-9]\\d*(\\.\\d+)?)$

Which will match

0.1
0.01
0.010
0.10
1.0
1.1
1.01
1.010
3

but not

0
0.0
-0.0
-1
-0.1