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

If you want to check if a number (positive) has one dot and if you want to use regex, you must escape the dot, because the dot means "any char" :-)

see http://docs.oracle.com/javase/6/docs/api/java/util/regex/Pattern.html

Predefined character classes
.   Any character (may or may not match line terminators)
\d  A digit: [0-9]
\D  A non-digit: [^0-9]
\s  A whitespace character: [ \t\n\x0B\f\r]
\S  A non-whitespace character: [^\s]
\w  A word character: [a-zA-Z_0-9]
\W  A non-word character: [^\w]

so you can use something like

System.out.println(s.matches("[0-9]+\\.[0-9]+"));

ps. this will match number such as 01.1 too. I just want to illustrate the \\.