package rocks.zipcode; import java.io.IOException; /** * @author leon on 16/11/2018. */ public class AlphaCharDocument extends Document { public AlphaCharDocument(String fileName) throws IOException { super(fileName); } @Override public void write(String contentToBeWritten) { if (isAlpha(contentToBeWritten)){ super.write(contentToBeWritten); }else{ throw new IllegalArgumentException(); } } private Boolean isAlpha(String s) { return (s.matches("[a-zA-z ]+")); } }