Question

When I run this program, the window blocks out the buttons in panel2 when I use setSize to determine window size.

In addition, if I use frame.pack() instead of setSize(), all components are on one horizontal line but I’m trying to get them so that panel1 components are on one line and panel2 components are on a line below them.

Could someone explain in detail the answers to both of these problems?

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Exercise16_4 extends JFrame{
    // FlowLayout components of top portion of calculator
    private JLabel jlbNum1 = new JLabel("Number 1");
    private JTextField jtfNum1 = new JTextField(4);
    private JLabel jlNum2 = new JLabel("Number 2");
    private JTextField jtfNum2 = new JTextField(4);
    private JLabel jlbResult = new JLabel("Result");
    private JTextField jtfResult = new JTextField(8);

    // FlowLayout Components of bottom portion of calculator
        private JButton jbtAdd = new JButton("Add");
    private JButton jbtSubtract = new JButton("Subtract");
    private JButton jbtMultiply = new JButton("Multiply");
    private JButton jbtDivide = new JButton("Divide");


    public Exercise16_4(){
        JPanel panel1 = new JPanel();
        panel1.setLayout(new FlowLayout(FlowLayout.CENTER, 3, 3));
        panel1.add(jlbNum1);
        panel1.add(jtfNum1);
        panel1.add(jlNum2);
        panel1.add(jtfNum2);
        panel1.add(jlbResult);
        panel1.add(jtfResult);

        JPanel panel2 = new JPanel();
        panel2.setLayout(new FlowLayout(FlowLayout.CENTER, 3, 10));
        panel1.add(jbtAdd);
        panel1.add(jbtSubtract);
        panel1.add(jbtMultiply);
        panel1.add(jbtDivide);

        add(panel1, BorderLayout.NORTH);
        add(panel2, BorderLayout.CENTER);
    }

    public static void main(String[] args){
        Exercise16_4 frame = new Exercise16_4();

        frame.setTitle("Caculator");
        frame.setSize(400, 200);
        frame.setLocationRelativeTo(null);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        //frame.setResizable(false);
        frame.setVisible(true);
    }
}

Answer 1

You’re problem is likely a typographical error in that you’re adding all components to panel1 and none to panel2:

  // you create panel2 just fine
  JPanel panel2 = new JPanel();
  panel2.setLayout(new FlowLayout(FlowLayout.CENTER, 3, 10));

  // but you don't use it! Change below to panel2.
  panel1.add(jbtAdd);
  panel1.add(jbtSubtract);
  panel1.add(jbtMultiply);
  panel1.add(jbtDivide);

Add the buttons to panel2, and then call pack() before setVisible(true). Do not set the size of the GUI.