hex2String

import java.io.UnsupportedEncodingException;

public class Caculator {

    public static String toBytes(String str) throws UnsupportedEncodingException {
        if(str == null || str.trim().equals("")) {
            return new String(new byte[0], "utf-8");
        }
        byte[] bytes = new byte[str.length() / 2];
        for(int i = 0; i < str.length() / 2; i++) {
            String subStr = str.substring(i * 2, i * 2 + 2);
            bytes[i] = (byte) Integer.parseInt(subStr, 16);
        }
        return new String(bytes, "utf-8");
    }

    public static void main(String[] args) throws UnsupportedEncodingException {
        System.out.println(toBytes(args[0]));
    }
}

javac Caculator.java
java Caculator 6e616d652d3ee5a2a80a71712d3e3234333535383636