<h:form>
   <h:dataTable value="#{commingMaanagedBean.dmbrb}" var="o" binding="#{table}">


            <h:column>
                 <h:inputText  value="#{amountUpdatingManagedBean.list[table.rowIndex]}" disabled="#{o.dvariable}"/>

            </h:column>
    </h:dataTable>
            <h:commandButton value="UPDATE" action="#{amountUpdatingManagedBean.clearamount}" />

    </h:form>

@ManagedBean
 @RequestScoped
 public class AmountUpdatingManagedBean {

  private String username;
  private List<String> list;



   public String getUsername() {
    return username;
  }

   public List<String> getList() {
    return list;
   }

   public void setList(List<String> list) {
    this.list = list;
   }

    public void setUsername(String username) {
    this.username = username;
    }
    public String clearamount(){

    if(list.isEmpty()){
         System.out.println("the list is empty ");
     }
     else {
        System.out.println("the list is pragent");

     }
     return null;
     }
    }