How to validate email & uploaded file in java?

How to validate email in java?

import javax.faces.context.FacesContext;
import javax.faces.component.UIComponent;
import javax.faces.validator.ValidatorException; 

public void validateEmail (FacesContext context, UIComponent toValidate, Object value) throws ValidatorException {
        String eMail = (String) value;
        if (!"".equals(eMail)) {
            if (eMail.indexOf("@") < 0) {
                FacesMessage message = new FacesMessage("Invalid email address!");
                throw new ValidatorException(message);
            }
        }
    }


//Using the above method with primefaces input text field
<p:inputText id="memail" value="#{addmem.memail}"  validator="#{user.validateEmail}"  required="false" label="memail" size="35"  />

How to validate uploaded file or check file existence in disk in java?

import javax.faces.validator.ValidatorException;
import javax.faces.context.FacesContext;
import javax.faces.component.UIComponent; import javax.faces.context.ExternalContext;

import org.primefaces.model.UploadedFile;

public void validateFile(FacesContext context, UIComponent toValidate, Object value) throws ValidatorException {
 ServletContext servletContext = (ServletContext) FacesContext.getCurrentInstance().getExternalContext().getContext();

        UploadedFile uFile = (UploadedFile) value;

       String uploadfilename = uFile.getFileName().substring(uFile.getFileName().lastIndexOf("\\") + 1, uFile.getFileName().length());
       

       String serverfileaddress = servletContext.getRealPath("") + File.separator + testlabConstants.FOLDER_NAME_OF_UPLOADED_FILE + File.separator + uploadfilename;

         File f = new File(serverfileaddress);

            if (f.exists()) {
            FacesMessage message = new FacesMessage("File already exist !");
            throw new ValidatorException(message);
        }

    }

 // Using the above method with primefaces file upload component

  <p:fileUpload label="Upload File" id="uploadfile" validator="#{tdbean.validateFile}" required="true" value="#{tdbean.file}"   mode="simple"/>