Decimal or numeric values in regular expression validation

Question

I am trying to use a regular expression validation to check for only decimal values or numeric values. But user enters numeric value, it don\'t be first digit \"0\"

Answer 1

I've tested all given regexes but unfortunately none of them pass those tests:

    String []goodNums={"3","-3","0","0.0","1.0","0.1"};
    String []badNums={"001","-00.2",".3","3.","a",""," ","-"," -1","--1","-.1","-0", "2..3", "2-", "2...3", "2.4.3", "5-6-7"};

Here is the best I wrote that pass all those tests:

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