Why does my components go out of boundaries, pleas

  import net.java.dev.designgridlayout.Tag;
  import net.java.dev.designgridlayout.DesignGridLayout;
  import javax.swing.table.DefaultTableModel;  
  import javax.swing.*;
  import javax.swing.event.*; 
  import java.awt.*;
  import java.awt.event.*;

  class alignmentprob 
  {
  JFrame JF;
  Container C,C5;
  JDesktopPane JDP;
  JInternalFrame JIF5;
  JLabel i5l1,i5l2,i5l3,i5l4,i5l5,i5l6,i5l7;
  JTextField i5t1,i5t2,i5t3;
  JComboBox<String> i5cb1;
  JButton i5b1,i5b2,i5b3;
  JSeparator i5sep1,i5sep2,i5sep3,i5sep4,i5sep5,i5sep6;
  JTable i5Table1;
  DefaultTableModel i5Model;
  String[] i5Credit = {"A","B"};
  String[] i5ColumnNames = {"Name","Qty","Rate/kg","rate/dzn","total amt."};
  JScrollPane i5t1sp1;

  public alignmentprob()
  {
  JF = new JFrame();
  JDP = new JDesktopPane();
  JF.setVisible(true);
  JF.setSize(800,600);
  JIF5 = new JInternalFrame("Daily Analysis",true,true, true, true);  
  C=JF.getContentPane();
  C.add(JDP,BorderLayout.CENTER);
  JIF5.setVisible(true);
  JIF5.setBounds(10, 10, 600, 500); 
  C5 = JIF5.getContentPane();
  DesignGridLayout layout5 = new DesignGridLayout(C5);

i5l1 = new JLabel("FREIGHT DETAILS");
i5l2 = new JLabel("Date : ");

i5l3 = new JLabel("SALE DETAILS");
i5l4 = new JLabel("Cash Sales :                             Rs. ");
i5l5 = new JLabel("Credit :  ");

i5l6 = new JLabel("EXPENSES");
i5l7 = new JLabel("Food & Tea :                            Rs. ");


i5t1 = new JTextField(20);
i5t2 = new JTextField(20);
i5t3 = new JTextField(20);

i5cb1 = new JComboBox<String>(i5Credit);

i5b1 = new JButton("Save");
i5b2 = new JButton("Reset"); 
i5b3 = new JButton("Close");

i5sep1 = new JSeparator();
i5sep2 = new JSeparator();  
i5sep3 = new JSeparator();
i5sep4 = new JSeparator();
i5sep5 = new JSeparator();
i5sep6 = new JSeparator();

i5Model = new DefaultTableModel(i5ColumnNames,5);
i5Table1 =new JTable(i5Model){@Override
public boolean isCellEditable(int arg0, int arg1)
{
return false;
}
       };


i5t1sp1 = new JScrollPane(i5Table1);


layout5.row().left().add(i5sep1).fill().withOwnRowWidth();
layout5.row().center().add(i5l1);
layout5.row().left().add(i5sep2).fill().withOwnRowWidth();
layout5.row().grid(i5l2).add(i5t1);

layout5.row().left().add(i5sep3).fill().withOwnRowWidth();
layout5.row().center().add(i5l3);
layout5.row().left().add(i5sep4).fill().withOwnRowWidth();
layout5.row().grid(i5l4).add(i5t2);
layout5.row().grid(i5l5).add(i5cb1);
layout5.row().left().add(i5t1sp1);

layout5.row().left().add(i5sep5).fill().withOwnRowWidth();
layout5.row().center().add(i5l6);
layout5.row().left().add(i5sep6).fill().withOwnRowWidth();
layout5.row().grid(i5l7).add(i5t3);
layout5.row().center().add(i5b1).add(i5b2).add(i5b3);

JDP.add(JIF5);
}

public static void main(String args[])
{
 new alignmentprob();
}
}

My problem is that the textfields are too long and go out of bounds. The table I made consists of 5 rows, but it tends to take up more space. I actually wanted to align the FREIGHT DETAILS & SALES DETAILS in parallel, separated using a vertical line. Please help me with code to do all this, so that my form looks neat and is fully visible.

My problem is that the textfields are too long and go out of bounds.

I wasn't able to reproduce the issue based on the code you've posted. Maybe there's something else I'm not seeing that causes this behaviour.

I actually wanted to align the FREIGHT DETAILS & SALES DETAILS in parallel, separated using a vertical line.

Even when working with third-party layout managers such as DesignGridLayout you can follow a Nested Layout approach using JPanel's to group Freight details and Sales detail components.

About the vertical separator, don't think it's possible with DesignGridLayout. While you can have components spanning several rows it doesn't work with JSeparator.

Please help me with code to do all this, so that my form looks neat and is fully visible.

StackOverflow is not a code factory so in most cases people won't do your job for you but they can provide useful examples. However as I've had to copy all your code to test it and I've made some changes using nested layouts approach, I'll make an exception here. Hope it be helpful:

import javax.swing.JButton;
import javax.swing.JComboBox;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JSeparator;
import javax.swing.JTable;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.table.DefaultTableModel;
import net.java.dev.designgridlayout.DesignGridLayout;

public class Demo {

    private void createAndShowGUI() {

        JLabel i5l1 = new JLabel("FREIGHT DETAILS");
        JLabel i5l2 = new JLabel("Date : ");
        JLabel i5l3 = new JLabel("Vehicle No. : ");
        JLabel i5l4 = new JLabel("From : ");
        JLabel i5l5 = new JLabel("Item : ");
        JLabel i5l6 = new JLabel("Quantity : ");
        JLabel i5l7 = new JLabel("Kg.");
        JLabel i5l8 = new JLabel("Rate :                                          Rs.");
        JLabel i5l15 = new JLabel("SALE DETAILS");
        JLabel i5l16 = new JLabel("Cash Sales :                             Rs. ");
        JLabel i5l17 = new JLabel("Credit :                                       Rs. ");
        JLabel i5l18 = new JLabel("EXPENSES");
        JLabel i5l19 = new JLabel("Food & Tea :                            Rs. ");
        JLabel i5l20 = new JLabel("Wages :                                   Rs. ");
        JLabel i5l21 = new JLabel("Miscellaneous Expenses :     Rs. ");

        JTextField i5t1 = new JTextField(20);
        JTextField i5t2 = new JTextField(20);
        JTextField i5t3 = new JTextField(20);
        JTextField i5t4 = new JTextField(20);
        JTextField i5t11 = new JTextField(20);
        JTextField i5t12 = new JTextField(20);
        JTextField i5t13 = new JTextField(20);
        JTextField i5t14 = new JTextField(20);

        JComboBox i5cb1 = new JComboBox<>();
        JComboBox i5cb2 = new JComboBox<>();
        JComboBox i5cb3 = new JComboBox<>();

        JButton i5b1 = new JButton("Save");
        JButton i5b2 = new JButton("Reset"); 
        JButton i5b3 = new JButton("Close");

        JSeparator i5sep1 = new JSeparator();
        JSeparator i5sep2 = new JSeparator();
        JSeparator i5sep3 = new JSeparator();
        JSeparator i5sep4 = new JSeparator();
        JSeparator i5sep5 = new JSeparator();
        JSeparator i5sep6 = new JSeparator();

        Object[] columnNames = new Object[]{"Column # 1", "Column # 2", "Column # 3", "Column # 4"};
        DefaultTableModel model = new DefaultTableModel(columnNames, 10);
        JTable table = new JTable(model);

        JScrollPane i5t1sp1 = new JScrollPane(table);

        JPanel freightPanel = new JPanel();
        DesignGridLayout layout1 = new DesignGridLayout(freightPanel);

        layout1.row().left().add(i5sep1).fill().withOwnRowWidth();
        layout1.row().center().add(i5l1);
        layout1.row().left().add(i5sep2).fill().withOwnRowWidth();
        layout1.row().grid(i5l2).add(i5t1);
        layout1.row().grid(i5l3).add(i5t2);
        layout1.row().grid(i5l4).add(i5cb1);
        layout1.row().grid(i5l5).add(i5cb2);
        layout1.row().grid(i5l6).add(i5t3).add(i5l7);
        layout1.row().grid(i5l8).add(i5t4);

        layout1.row().left().add(i5sep5).fill().withOwnRowWidth();
        layout1.row().center().add(i5l18);
        layout1.row().left().add(i5sep6).fill().withOwnRowWidth();
        layout1.row().grid(i5l19).add(i5t12);
        layout1.row().grid(i5l20).add(i5t13);
        layout1.row().grid(i5l21).add(i5t14);

        JPanel salePanel = new JPanel();
        DesignGridLayout layout2 = new DesignGridLayout(salePanel);

        layout2.row().left().add(i5sep3).fill().withOwnRowWidth();
        layout2.row().center().add(i5l15);
        layout2.row().left().add(i5sep4).fill().withOwnRowWidth();
        layout2.row().grid(i5l16).add(i5t11);
        layout2.row().grid(i5l17).add(i5cb3);
        layout2.row().grid().add(i5t1sp1);

        JInternalFrame internalFrame = new JInternalFrame("Daily Analysis",true,true, true, true);        

        DesignGridLayout mainLayout = new DesignGridLayout(internalFrame.getContentPane());
        mainLayout.row().grid().add(freightPanel).add(salePanel);
        mainLayout.row().left().add(new JSeparator()).fill().withOwnRowWidth();
        mainLayout.row().center().add(i5b1).add(i5b2).add(i5b3);

        internalFrame.pack();
        internalFrame.setVisible(true);

        JFrame frame = new JFrame("Demo");
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);
        frame.getContentPane().add(internalFrame);
        frame.pack();
        frame.setLocationRelativeTo(null);
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Demo().createAndShowGUI();
            }
        });
    }
}