用于字符串验证的正则表达式

Question

I need a regex for validating the String that comes in pattern like NBTAAA-PREM_001 and NBTAAA_001

The NBTAAA part can be numbers or alphabets or alphanumeric, optionally followed by the fixed string -PREM (hyphen PREM), then underscore _ , followed by three alphanumeric characters.

For this "NBTAAA_001", need regex without '-PREM' (hyphen PREM).

I have written the code:

public static void main(String[] args) {
    List<String> input = new ArrayList<String>();

    input.add("NBTAAA-PRIM_001");
    input.add("NBTAAA_001");

    for (String ssn : input) {
        //  String ssn = "NBTAAA-PRIM_001";
        if (ssn.indexOf("-") != -1) {
            int PRIMbeginIndex = ssn.indexOf("-") + 1;
            int PRIMEndIndex = PRIMbeginIndex + 4;

            String d = ssn.substring(PRIMbeginIndex, PRIMEndIndex);

            if (d.equalsIgnoreCase("PRIM")) {

                if (ssn.matches("^([A-Za-z0-9]+(?=.*?\bPRIM\b)+_[A-Za-z0-9]{3})$")) {
                    System.out.println(" PRIM image value : " + ssn);
                }
            }
        }
        else {
            if (ssn.matches("^([A-Za-z0-9]+_[A-Za-z0-9]{3})$")) {
                System.out.println("NORMAL IMAGE value : " + ssn);
            }
        }  
    }
} 

But it is not working properly. Please help me to resolve this.

Answer 1

^[a-zA-Z0-9]+(?:-PREM)?_[a-zA-Z0-9]{3}$

You can try this.See demo.

http://regex101.com/r/iM2wF9/16