What you seem to asking for is a factory pattern
public interface ISign {
public void operation1();
public void operation2();
}
and a Factory class to generate classes based on input
public class SignGenerator {
public static ISign getSignObject(String str1,String str2, String str3, String str4) {
if(str1.equals("blah blah"))
return new FirstType();
if(str1.equals("blah blah2") && str2.equals("lorem ipsum"))
return new SecondType();
return new ThirdType();
}
}
public class FirstType implements ISign {
}
public class SecondType implements ISign {
}
public class ThirdType implements ISign {
}
Implement all Type specific logic in these classes so you can call them without checking with tons of if..else clauses first