JScrollPane not appearing, elements overflowing

Question 1

BorderLayout has five defined locations onto which components can be added...

enter image description here

The default location is CENTER.

Basically what is happening, when you add each component to the frame/content pane, it's removing the last one and placing it self in the middle, as only one component can exist within a give location.

Start by changing the layout manager. Take a look at A Visual Guide to Layout Managers for some ideas

Question 2

When using BorderLayout setBounds() method does not have any effect. Using BorderLayout,
you can fix your components only in five position North, South, East, West and Center
If you does not specify position like add(comp, BorderLayout.EAST), it will render your components
randomly. Adding more components without specifying position will get overlapped and it wont give clear view.

You are using more than five components and you are not specifying positions, so scrollpane
is not coming.

Use GridBagLayout to yield correct result. Refer http://docs.oracle.com/javase/tutorial/uiswing/layout/gridbag.html

Question 3

Remove this line:

mygui.getContentPane();

cause it does not thing. Also, change

mygui.setLayout(new BorderLayout()); //playing with layout here

to

mygui.getContentPane ().setLayout (null); // playing with layout here

cause you want to specify bounds for all components yourself. Also change

myarea.setBounds(200, 50, 250, 200);

to

scrolla.setBounds(200, 50, 250, 200);

and remove the following line:

scrolla.setPreferredSize(new Dimension(250, 200));

because without layout manager you don't need preferred size. Also change

mygui.add(first);
mygui.add(second);
mygui.add(third);
mygui.add(fourth);
mygui.add(fifth);
mygui.add(sixth);
mygui.add(seventh);

mygui.add(myint);
mygui.add(myfloat);
mygui.add(myshort);
mygui.add(mylong);
mygui.add(mybyte);
mygui.add(mydbl);
mygui.add(mybool);
mygui.add(scrolla);

to

mygui.getContentPane ().add(first);
mygui.getContentPane ().add(second);
mygui.getContentPane ().add(third);
mygui.getContentPane ().add(fourth);
mygui.getContentPane ().add(fifth);
mygui.getContentPane ().add(sixth);
mygui.getContentPane ().add(seventh);

mygui.getContentPane ().add(myint);
mygui.getContentPane ().add(myfloat);
mygui.getContentPane ().add(myshort);
mygui.getContentPane ().add(mylong);
mygui.getContentPane ().add(mybyte);
mygui.getContentPane ().add(mydbl);
mygui.getContentPane ().add(mybool);
mygui.getContentPane ().add(scrolla);

cause components should not be added directly to JFrame, but only to its content pane. After these changes it should work fine. You will see scroll bars once you have enough text in your text area. Here is fixed verion of your code that works for me:

import java.awt.Color;
import java.awt.Dimension;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class Example
{
    public static void main (String [] args)
    {

        JFrame mygui = new JFrame ();
        mygui.getContentPane ();
        mygui.setBounds (100, 100, 700, 500);
        mygui.getContentPane ().setLayout (null); // playing with layout here

        JLabel first = new JLabel ("integer:");
        JLabel second = new JLabel ("float:");
        JLabel third = new JLabel ("short:");
        JLabel fourth = new JLabel ("long:");
        JLabel fifth = new JLabel ("byte:");
        JLabel sixth = new JLabel ("double:");
        JLabel seventh = new JLabel ("boolean:");
        JTextField myint = new JTextField ("a");
        JTextField myfloat = new JTextField ("b");
        JTextField myshort = new JTextField ("c");
        JTextField mylong = new JTextField ("d");
        JTextField mybyte = new JTextField ("e");
        JTextField mydbl = new JTextField ("f");
        JTextField mybool = new JTextField ("g");
        JTextArea myarea = new JTextArea ();
        JScrollPane scrolla = new JScrollPane (myarea);

        first.setOpaque (true);
        first.setBounds (20, 20, 50, 20);
        second.setOpaque (true);
        second.setBounds (20, 70, 50, 20);
        third.setOpaque (true);
        third.setBounds (20, 120, 50, 20);
        fourth.setOpaque (true);
        fourth.setBounds (20, 170, 50, 20);
        fifth.setOpaque (true);
        fifth.setBounds (20, 220, 50, 20);
        sixth.setOpaque (true);
        sixth.setBounds (20, 270, 50, 20);
        seventh.setOpaque (true);
        seventh.setBounds (20, 320, 50, 20);

        myint.setBounds (70, 20, 50, 20);
        myint.setOpaque (true);
        myfloat.setBounds (70, 70, 50, 20);
        myfloat.setOpaque (true);
        myshort.setBounds (70, 120, 50, 20);
        myshort.setOpaque (true);
        mylong.setBounds (70, 170, 80, 20);
        mylong.setOpaque (true);
        mybyte.setBounds (70, 220, 50, 20);
        mybyte.setOpaque (true);
        mydbl.setBounds (70, 270, 50, 20);
        mydbl.setOpaque (true);
        mybool.setBounds (70, 320, 50, 20);
        mybool.setOpaque (true);

        myarea.setOpaque (true);
        myarea.setBackground (Color.yellow);
        scrolla.setBounds (200, 50, 250, 200);
        scrolla.setPreferredSize (new Dimension (250, 200));

        mygui.getContentPane ().add (first);
        mygui.getContentPane ().add (second);
        mygui.getContentPane ().add (third);
        mygui.getContentPane ().add (fourth);
        mygui.getContentPane ().add (fifth);
        mygui.getContentPane ().add (sixth);
        mygui.getContentPane ().add (seventh);

        mygui.getContentPane ().add (myint);
        mygui.getContentPane ().add (myfloat);
        mygui.getContentPane ().add (myshort);
        mygui.getContentPane ().add (mylong);
        mygui.getContentPane ().add (mybyte);
        mygui.getContentPane ().add (mydbl);
        mygui.getContentPane ().add (mybool);
        mygui.getContentPane ().add (scrolla);

        myarea.append ("sdfgsdfgsdfgsf\n");

        mygui.setVisible (true);
        mygui.setDefaultCloseOperation (JFrame.EXIT_ON_CLOSE);
    }
}