anchorTagValidator.java

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class AnchorTagValidator{

   private Pattern pattern;
   private Matcher matcher;

   private static final String HTML_TAG_PATTERN = "<a(?=\s|>)(?!(?:[^>=]|=(['"])(?:(?!\1).)*\1)*?\shref=['"])[^>]*>.*?<\/a>";

   public AnchorTagValidator(){
	  pattern = Pattern.compile(HTML_TAG_PATTERN);
   }

  public boolean validate(final String tag){

	  matcher = pattern.matcher(tag);
	  return matcher.matches();

  }
}