Question

I have the following code:

String table;
private DB.ConnectMAS mas=new DB.ConnectMAS();
java.sql.ResultSet rs1 = mas.DBquery("select * from products");


try{ 
String duedate = "";
while(rs1.next()){
    String duedate = rs1.getString("duedate");
table+="<tr><td>"+duedate.substring(1,10)+"</td></tr>"; 
} catch(java.sql.SQLException e){}

It is throwing an error on duedate.substring(1,10)

I’m trying to understand why this is incorrect?
thanks in advance

error:

SEVERE: Servlet.service() for servlet POList threw exception
java.lang.NullPointerException
    at POList.getDetails(POList.java:126)
    at POList.getTable(POList.java:165)
    at POList.processRequest(POList.java:55)
    at POList.doGet(POList.java:177)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:269)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:188)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:210)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:174)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:108)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
    at org.apache.coyote.http11.Http11AprProcessor.process(Http11AprProcessor.java:834)
    at org.apache.coyote.http11.Http11AprProtocol$Http11ConnectionHandler.process(Http11AprProtocol.java:640)
    at org.apache.tomcat.util.net.AprEndpoint$Worker.run(AprEndpoint.java:1286)
    at java.lang.Thread.run(Unknown Source)

Answer 1

Like @danben says, you need to post the error to get meaningful help. Looking at your code, though, I’d imagine that duedate at the time of the error is null. You probably need to move the code that’s actually using duedate inside your while loop.