使用正则表达式Java匹配数字和字母/数字（分隔）

Question

what it's the correct form to match when an String is number o letters/number, for example, I have this code

String regexNum = "\\d*";
String regexVar = "[a-zA-Z0-9]*";

if(valor.matches(regexNum))
{
   System.out.println("It's a number");
}
if(valor.matches(regexVar))
{
   System.out.println("It's a variable");
}

When I enter for example "SAL45", the output is "It's a variable", what's fine, so, when a I enter "45", the output is "It's a variable" again but I need to output be "It's a number", how can I fix that mistake?

Answer 1

With "45", both messages are printed. You just need to make use of else to show only one message. Here's the corrected code:-

String regexNum = "\\d*";
String regexVar = "[a-zA-Z0-9]*";

if(valor.matches(regexNum))
{
   System.out.println("It's a number");
}
else if(valor.matches(regexVar))
{
   System.out.println("It's a variable");
}

Answer 2

Your regex is not correct.

Here is the Condition for Number :

1. Length Must greater than zero
2. All there character should be digits

And Here is the Condition for a Variable :

1. Must Start with _ or Alphabet [a-zA-Z] or $
2. Other Character Should be _ , Number[0-9], Alphabet[a-zA-Z], $

String regexNum = "\\d+";
    String regexVar = "[a-zA-Z_$][a-zA-Z_$0-9]*";

    if (valor.matches(regexNum)) {
        System.out.println("It's a number");
    }
    if (valor.matches(regexVar)) {
        System.out.println("It's a variable");
    }