public class MyClass {
    static String extract_only_characters_numbers(String s) { 
        int len = s.length(); 
        String regx = "[a-zA-Z0-9]"; 
        String characters_numbers = "";
          
        for (int i = 0; i < len; i++) { 
            char ch = s.charAt(i); 
            if (String.valueOf(ch).matches(regx))  
               characters_numbers = characters_numbers + ch; 
        } 
        return characters_numbers; 
    } 
    public static void main(String args[]) {
        String s = "c++14$vb.net&%java*() php <>/python 3.7.3"; 
          
        System.out.println(extract_only_characters_numbers(s)); 
    }
}
  
  
  
/*
run:
  
c14vbnetjavaphppython373
  
*/