CODEWITHSUNDEEP
javajsparraylistjstl
tiddi rastogi
tiddi rastogi

Reputation: 526

Prevent display of Arraylist values twice in java

I have a method which returns an arraylist. But the Arraylsit is displaying its values twice. The code is-

ArrayList<Double> ref_jsp=new ArrayList<Double>();

public  ArrayList<Double> refernece(String name) throws SQLException, ParseException {

    String first=name.substring(1,19);
    String last =name.substring(24,42);
   List<Double> slist = new ArrayList<Double>(map1.keySet());
  String s = StringUtils.join(slist, ',');
  System.out.println("comma separated string"+s);

       try
            {  
              con = getConnection();
              stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_READ_ONLY);

             String vs2="SQL Query"
             stmt.executeQuery(vs2);
             rs1 = stmt.getResultSet();

             while(rs1.next()) 
                {
                   ref_jsp.add((rs1.getDouble(1)));
                   ref_jsp.add((rs1.getDouble(2)));
                   ref_jsp.add((rs1.getDouble(3)));
                   ref_jsp.add((rs1.getDouble(4)));
                   ref_jsp.add((rs1.getDouble(5)));
                   ref_jsp.add((rs1.getDouble(6)));
                   ref_jsp.add(rs1.getDouble(7));
                   ref_jsp.add(rs1.getDouble(8));
                   ref_jsp.add(rs1.getDouble(9));
                   ref_jsp.add(rs1.getDouble(10));
                   ref_jsp.add((rs1.getDouble(11)));

            }  
         }
        catch( Exception e )
                {
                    System.out.println("\nException in reference "+e);
                }
        return ref_jsp;
    }

My Sql query is fine.I checked it.The values returned by ref_jsp are displayed twice.Please explain where I'm going wrong??My jsp code foe displaying list values is-

<%
 String ref_name= request.getParameter("ref_logtime");
 pageContext.setAttribute("ref_name", ref_name);
 ref.FindClosestToMultiplesOfTen(ref_name);
 ref.refernece(ref_name);
%>
<table width = "300px" border = "1" cellspacing="2">

 <tr><c:forEach var="r" items="${ref.refernece(param.ref_logtime)}"> 
 <td><c:out value="${r}"></c:out></td>
 </c:forEach></tr>
 </table>

My output is of the form-

 value-1 value-2 value-3 value-4 value-1 value-2 value-3 value-4

Upvotes: 3

Views: 1614

Answers (2)

busybug91
busybug91

Reputation: 241

@Zeeshan pointed the mistake correctly. If you don't want to the make the arraylist being returned as a local member of the function and as you mentioned ref_jsp is being used in another method also, make sure to clear the elements of arraylist when all your associated methods are done operating on that list. Use ref_jsp.clear() for that.

Upvotes: 0

Zeeshan
Zeeshan

Reputation: 12421

It looks like problem is because of the following line in your java class.

ArrayList<Double> ref_jsp = new ArrayList<Double>();

You have declared ref_jsp as class level variable, move it inside the method public ArrayList<Double> refernece(String name).

It is happening because you are calling your referenece method twice from the jsp.

<%
 String ref_name= request.getParameter("ref_logtime");
 pageContext.setAttribute("ref_name", ref_name);
 ref.FindClosestToMultiplesOfTen(ref_name);
 ref.refernece(ref_name); //******* 1st call *********
%>
<table width = "300px" border = "1" cellspacing="2">

 <tr><c:forEach var="r" items="${ref.refernece(param.ref_logtime)}">//***2nd call*** 
 <td><c:out value="${r}"></c:out></td>
 </c:forEach></tr>
 </table>

During the 1st call suppose you got 10 items and those got added in your arraylist, and since that arraylist is a instance level variable, during the second call you again got 10 items and that got added along with the existing 10, hence you are having duplicate items.

Upvotes: 2

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