exceptions-readandwrite/src/main/java/rocks/zipcode/NumericCharDocument.java

package rocks.zipcode;

import java.io.IOException;

/**
 * @author leon on 16/11/2018.
 */
public class NumericCharDocument extends Document {
    public NumericCharDocument(String fileName) throws IOException {
        super(fileName);
    }

    @Override
    public void write(String contentToBeWritten) {
        if (isNumeric(contentToBeWritten)) {
            super.write(contentToBeWritten);
        } else throw new IllegalArgumentException();
    }

    private Boolean isNumeric(String s) {

        return s.matches("[0-9]*");
    }
}