Advanced Java Programming - Old Questions

2. What is layout management? Discuss any three layout management classes with example of each.

The layout management is used to arrange components in a particular manner. The Java LayoutManagers facilitates us to control the positioning and size of the components in GUI forms. The layout management classes are given below:

1. Border Layout

The BorderLayout is used to arrange the components in five regions: north, south, east, west and center. Each region (area) may contain one component only.

Components of the BorderLayout Manager

·         BorderLayout.NORTH

·         BorderLayout.SOUTH

·         BorderLayout..EAST

·         BorderLayout.WEST

·         BorderLayout.CENTER

BorderLayout Constructors:

Example:

import java.awt.BorderLayout;  

import javax.swing.JButton;

import javax.swing.JFrame;

public class BorderLayoutExample {  

BorderLayoutExample(){  

    JFrame f=new JFrame();  

    JButton b1=new JButton("NORTH");;  

    JButton b2=new JButton("SOUTH");;  

    JButton b3=new JButton("EAST");;  

    JButton b4=new JButton("WEST");;  

    JButton b5=new JButton("CENTER");;  

    f.add(b1,BorderLayout.NORTH);  

    f.add(b2,BorderLayout.SOUTH);  

    f.add(b3,BorderLayout.EAST);  

    f.add(b4,BorderLayout.WEST);  

    f.add(b5,BorderLayout.CENTER);  

    f.setSize(300,300);  

    f.setVisible(true);  

}  

public static void main(String[] args) {  

    new BorderLayoutExample();  

}  

}  

2. Flow Layout

The FlowLayout is used to arrange the components in a line, one after another (in a flow).  It arranges components in a line, if no space left remaining components goes to next line. Align property determines alignment of the components as left, right, center etc.

FlowLayout Constructors:

import java.awt.FlowLayout;

import javax.swing.JButton;

import javax.swing.JFrame;

public class FlowLayoutExample {

 FlowLayoutExample(){

     JFrame f = new JFrame("Flow Layout");

        JButton b1 = new JButton("button 1");

        JButton b2 = new JButton("button 2");

        JButton b3 = new JButton("button 3");

        JButton b4 = new JButton("button 4");

        JButton b5 = new JButton("button 5");

        f.add(b1);

        f.add(b2);

        f.add(b3);

        f.add(b4);

        f.add(b5);

        f.setLayout(new FlowLayout());

        f.setSize(300,300);  

        f.setVisible(true);  

    }

    public static void main(String[] args) {

        new FlowLayoutExample();

    }

}

3. Grid Layout

The GridLayout is used to arrange the components in rectangular grid. One component is displayed in each rectangle. Components are placed in columns and rows.

Every Component in a GridLayout has the same width and height. Components are added to a GridLayout starting at the top-left cell of the grid and proceeding left to right until the row is full. Then the process continues left to right on the next row of the grid, and so on.

GridLayout Constructors:

Example:

import java.awt.*;

import javax.swing.*;

public class GridDemo

{

      JButton b1, b2, b3, b4, b5, b6;

      GridDemo()

      {

           JFrame f = new JFrame("GridLayoutDemo");

           b1 = new JButton("A");

           b2 = new JButton("B");

           b3 = new JButton("C");

           b4 = new JButton("D");

           b5 = new JButton("E");

           b6 = new JButton("F");

           f.add(b1);

           f.add(b2);

           f.add(b3);

           f.add(b4);

           f.add(b5);

           f.add(b6);

           f.setLayout(new GridLayout(2, 3));

           f.setSize(200, 200);

           f.setVisible(true);

      }

      public static void main(String args[])

      {

           new GridDemo();

      }

}