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javajlabelderbyresultset

Can't get value from ResultSet to populate jLabel in Java

I am new to programming and trying to assign a value from a sql query to a jLabel. The program compiles and runs with no errors but doesn't change the jLabel. According to my research, this should work, but doesn't. DB connection is fine. When I debug, the problem seems to be with the line: double d = rs.getDouble(1); Here is my code:

String sum = "SELECT SUM(TOTAL) FROM PUNCHES WHERE EID = 1"; 

Statement st = con.createStatement();            
ResultSet rs = st.executeQuery(sum); //rs should have 1 row, 1 column

double d = rs.getDouble(1);
lblGrandTotal.setText(String.valueOf(d));

If I substitute an arbitrary value like 12.345 for d, it works.

Solution

  • You forgot to call rs.next()

    ResultSet rs = st.executeQuery(sum); //rs should have 1 row, 1 column
if (rs.next())
{
    double d = rs.getDouble(1);
    ...
}
else
    // Failed to get result, do something useful here