CODEWITHSUNDEEP
javastring
Hrach Ghapantsyan
Hrach Ghapantsyan

Reputation: 699

Saving the values of a string to another class and retrieving it

I am currently trying to save the values of a string to another class file in JAVA called Memory.JAVA. The reason why I am doing this is because variables are not saved outside the Try - Catch Blocks. Therefore I initiate the class in the try catch block by using this code:

Memory mem = new Memory();

And then when I want to save a string, I use the following:

 mem.brother1ID = "Whatever";

The reason why I am not creating it as a new String is because in the Memory class, I have already initiated this string. To test that this has been saved, I have used System.out.println to print out the result which in this case was "Whatever" but when I try to get the same result printed out in the same class, I get the result "null". Does anyone have any suggestions regarding my issue? Please feel free to comment below. Thanks!

UPDATE:

Some code posted below:

private void searchFieldKeyReleased(java.awt.event.KeyEvent evt) {                                        
    try {

        Memory mem = new Memory();

        String sql = "select * from userInfo where firstName= ? OR lastname = ?";
        pst=conn.prepareStatement(sql);
        pst.setString(1, searchField.getText());
        pst.setString(2, searchField.getText());

        rs=pst.executeQuery();

        if(rs.next()) {
            String firstName = rs.getString("firstName");
            String lastName = rs.getString("lastName");
            String placeOfResidence = rs.getString("placeOfResidence");
            String employmentStatus = rs.getString("employmentStatus");
            String currentEmployer = rs.getString("currentEmployer");
            String taxStatus = rs.getString("taxStatus");
            String dateOfBirth = rs.getString("dateOfBirth");
            String mother = rs.getString("mother");
            String father = rs.getString("father");
            String brother1 = rs.getString("brother1");
            String brother2 = rs.getString("brother2");
            String brother3 = rs.getString("brother3");
            String brother4 = rs.getString("brother4");
            String brother5 = rs.getString("brother5");
            String sister1 = rs.getString("sister1");
            String sister2 = rs.getString("sister2");
            String sister3 = rs.getString("sister3");
            String sister4 = rs.getString("sister4");
            String sister5 = rs.getString("sister5");
            mem.brother1ID = rs.getString("brother1ID");
            mem.brother2ID = rs.getString("brother2ID");
            mem.brother3ID = rs.getString("brother3ID");
            mem.brother4ID = rs.getString("brother4ID");
            mem.brother5ID = rs.getString("brother5ID");
            mem.sister1ID = rs.getString("sister1ID");
            mem.sister2ID = rs.getString("sister2ID");
            mem.sister3ID = rs.getString("sister3ID");
            mem.sister4ID = rs.getString("sister4ID");
            mem.sister5ID = rs.getString("sister5ID");
            mem.fatherID = rs.getString("fatherID");
            mem.motherID = rs.getString("motherID");
            System.out.println(mem.brother1ID);
            System.out.println(firstName + " " + lastName);
            firstNameField.setText(firstName);
            lastNameField.setText(lastName);
            placeOfResidenceField.setText(placeOfResidence);
            employmentStatusField.setText(employmentStatus);
            currentEmployerField.setText(currentEmployer);
            taxStatusField.setText(taxStatus);
            dateOfBirthField.setText(dateOfBirth);
            motherField.setText(mother);
            fatherField.setText(father);
            brothersField1.setText(brother1);
            brothersField2.setText(brother2);
            brothersField3.setText(brother3);
            brothersField4.setText(brother4);
            brothersField5.setText(brother5);
            sisterField1.setText(sister1);
            sisterField2.setText(sister2);
            sisterField3.setText(sister3);
            sisterField4.setText(sister4);
            sisterField5.setText(sister5);



        }

    } catch(Exception e) {
        JOptionPane.showMessageDialog(null, e);
    }
}

And this is when I try to get the same results of System.out.println as before: 

private void brotherViewButton1ActionPerformed(java.awt.event.ActionEvent evt) {                                                   
    try {

        Memory mem = new Memory();

        String sql = "select * from userInfo where id=?";
        pst=conn.prepareStatement(sql);
        String IDNO = mem.brother1ID;
        System.out.println(IDNO);
        pst.setString(1, IDNO);

        rs=pst.executeQuery();

        if(rs.next()) {
            String firstName = rs.getString("firstName");
            String lastName = rs.getString("lastName");
            String placeOfResidence = rs.getString("placeOfResidence");
            String employmentStatus = rs.getString("employmentStatus");
            String currentEmployer = rs.getString("currentEmployer");
            String taxStatus = rs.getString("taxStatus");
            String dateOfBirth = rs.getString("dateOfBirth");
            String mother = rs.getString("mother");
            String father = rs.getString("father");
            String brother1 = rs.getString("brother1");
            String brother2 = rs.getString("brother2");
            String brother3 = rs.getString("brother3");
            String brother4 = rs.getString("brother4");
            String brother5 = rs.getString("brother5");
            String sister1 = rs.getString("sister1");
            String sister2 = rs.getString("sister2");
            String sister3 = rs.getString("sister3");
            String sister4 = rs.getString("sister4");
            String sister5 = rs.getString("sister5");
            System.out.println(firstName + " " + lastName);
            firstNameField.setText(firstName);
            lastNameField.setText(lastName);
            placeOfResidenceField.setText(placeOfResidence);
            employmentStatusField.setText(employmentStatus);
            currentEmployerField.setText(currentEmployer);
            taxStatusField.setText(taxStatus);
            dateOfBirthField.setText(dateOfBirth);
            motherField.setText(mother);
            fatherField.setText(father);
            brothersField1.setText(brother1);
            brothersField2.setText(brother2);
            brothersField3.setText(brother3);
            brothersField4.setText(brother4);
            brothersField5.setText(brother5);
            sisterField1.setText(sister1);
            sisterField2.setText(sister2);
            sisterField3.setText(sister3);
            sisterField4.setText(sister4);
            sisterField5.setText(sister5);



        }

    } catch(Exception e) {
        JOptionPane.showMessageDialog(null, e);
    } 
}

Upvotes: 0

Views: 1674

Answers (2)

Philip Puthenvila
Philip Puthenvila

Reputation: 512

Please look at here

try {

    Memory mem = new Memory();

    String sql = "select * from userInfo where id=?";
    pst=conn.prepareStatement(sql);
    String IDNO = mem.brother1ID;
    System.out.println(IDNO);

You are creating the object of Memory and not setting any value. then you are trying to print the brotherId which will be null, all String variables will be initialised to null, that is why you are getting 'null'. what you can do is put the printing statement out of the try catch block at he bottom , if there are any records in your database, it will print out the last records brotherId.

Upvotes: 0

Craig Otis
Craig Otis

Reputation: 32054

The reason the value brother1ID in your Memory object is null is because you're using a new instance of that object.

I strongly recommend you read up on how object instances are scoped in Java, and what it means to create a new instance, versus using an existing one.

For example, when you do this:

Memory mem = new Memory();
mem.brother1ID = "1234";

mem = new Memory();
System.out.println(mem.brother1ID);

The value printed will be null. This is because you're using a new instance of that class. If you wanted to maintain the values throughout multiple method calls, your best bet might be to save the Memory object as an instance variable of whatever class contains the methods you've shown. i.e.:

private Memory memory = new Memory();

...

private void searchFieldKeyReleased(java.awt.event.KeyEvent evt) {
    // Use 'this.memory'
    this.memory.brother1ID = "1234";
    //(or)
    System.out.println(this.memory.brother1ID);
}

private void brotherViewButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    // Use 'this.memory'
}

Upvotes: 1

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