check if the record exists in database

or you could use a count:

String query = "select count(*) 
from dbo.soil_det where rm_id = ? and box_no = ?";

then after executing the query you get the count with

                   rs.getInt(1)

using that you can decide which info to show to the user

very First You have to get count using sql if count is greater than zero then do not insert records and show message like already exists and in else part insert record. see following example

private boolean findCount(int rm_id,String box_no)
{
      int count=0;
     //write query here 
     count = assign query result;
     //check count 
if(count>0)
{
     return false;//records exists
}else{
    return true;//records do not exists
}

}

public void insertData()
{
     if(findCount(1,"1")){//pass values
       //Write down your insert logic
     }else{
      JOptionPane.showMessageDialog(rootPane, "Records Already Exists");
     }
}

Note: Friend in Your Example you have not written the insert logic. only select was there

First you could add -- on the db table -- a unique constrain on the columns (rm_id, box_no), this is anyway a good thing to do.

Then you could simply try to insert the box and catch the exception and check if it is a violation of the unique constraint.

Another option (still keeping the unique constraint) would be to make a more complicated SQL insert statement that inserts only if not existing, you may google "sql insert if not exist" to find some examples...

You need to get the appropriate record from the ResultSet e.g.

boolean found = rs.getString(1).equals().txtboxno.getText());

At the moment you're simply comparing the ResultSet object itself to a string, and that won't work. The above pulls the first record from the ResultSet and performs the comparison on that (note: your datatype may be different and you may need rs.getInt(1) etc.)

Perhaps its sufficient in your case just to check if you have a ResultSet result (via rs.next())

simplified version

private void txtboxnoFocusLost(java.awt.event.FocusEvent evt) {
DBUtil util = new DBUtil();

try {
    Connection con = util.getConnection();
    PreparedStatement stmt = con.prepareStatement(
        "select box_no from dbo.soil_det where rm_id = ? and box_no = ?");
    stmt.setLong(1, Long.parseLong(tf_rm_id.getText()));
    stmt.setString(2, (txtboxno.getText()));       
    ResultSet rs=stmt.executeQuery();
    if(!rs.next()){
      JOptionPane.showMessageDialog(rootPane, "Record added");
    }else{
       JOptionPane.showMessageDialog(rootPane, "Record already exists");
    }
} catch (Exception ex) {
    Logger.getLogger(DATAENTRY.class.getName()).log(Level.SEVERE, null, ex);
}

• rs.next() followed by if condition returns true if the record exists in a table. if not, return false.