How to check a string contains only digits and one occurrence of a decimal point?

Question

My idea is something like this but I dont know the correct code

if (mystring.matches(\"[0-9.]+\")){
  //do something here
}else{
  //do something here
}
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Answer 1

I think using regexes complicates the answer. A simpler approach is to use indexOf() and substring():

int index = mystring.indexOf(".");
if(index != -1) {
    // Contains a decimal point
    if (mystring.substring(index + 1).indexOf(".") == -1) {
        // Contains only one decimal points
    } else {
        // Contains more than one decimal point 
    }
}
else {
    // Contains no decimal points 
}