Java – How to set textfield value based on combobox options in Java

comboboxjavajtextfieldswing

I've a table in database named customer that have attribute like code and name. I've called the value of the customer in other table and displayed it using combo-box. I've displayed the code in combo-box, and all I wanna do is when I choose the code in combo-box, value 'name' can be displayed in text-field , the 'name' appear based on code.

here is my code :

try {
        Connections con = new Connections();
        con.setConnections();
        String sql = "select * from customer";
        Statement stat = con.conn.createStatement();
        ResultSet rs=stat.executeQuery(sql);        
        while (rs.next()){
        cmb_custCode.addItem(rs.getString("custCode"));

        txt_custName.setText(rs.getString("custName")); // i'm confused in here, how can i call the name based on the code 
        }
}

 catch(Exception e){
    e.printStackTrace();
  }
 }

for example :

when the code 'B0001' is selected in the combobox, the Jtextfield must also display "Bob" , because code B0001 is belongs to Bob.

Best Answer

EDIT:

Ok. So let's say that you have a user Bob and his code is B001.

ItemStateChanged Method

...
String code = (String) cmb.getSelectedItem();
try{

String sql = "SELECT * FROM customer WHERE code='"+code"'"
PreparedStatement prst = con.prepareStatement();
ResultSet rs = prst.executeQuery(sql);
String name = "";

while(rs.next()){

name = rs.getString('name');
}
txt.setText(name);
}catch(Exception ex){
}

You shouldn't actually connect inside the itemStateChanged but this is just an example.

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Java – Is Java “pass-by-reference” or “pass-by-value”

Java is always pass-by-value. Unfortunately, when we deal with objects we are really dealing with object-handles called references which are passed-by-value as well. This terminology and semantics easily confuse many beginners.

It goes like this:

public static void main(String[] args) {
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In the above example, Fifi is the dog's name after call to foo(aDog) because the object's name was set inside of foo(...). Any operations that foo performs on d are such that, for all practical purposes, they are performed on aDog, but it is not possible to change the value of the variable aDog itself.

For more information on pass by reference and pass by value, consult the following SO answer: https://stackoverflow.com/a/430958/6005228. This explains more thoroughly the semantics and history behind the two and also explains why Java and many other modern languages appear to do both in certain cases.

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Map<String, String> map = ...
for (Map.Entry<String, String> entry : map.entrySet()) {
    System.out.println(entry.getKey() + "/" + entry.getValue());
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On Java 10+:

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    System.out.println(entry.getKey() + "/" + entry.getValue());
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