Java Drawing Bar Charts

What is Bar Chart

• A bar chart or bar graph is a chart or graph that presents categorical data with rectangular bars with heights or lengths proportional to the values that they represent.
• Bar graphs/charts provide a visual presentation of categorical data.
• The bars can be plotted vertically or horizontally. A vertical bar chart is called a line graph.

Java applets can be designed to display bar charts, which are used in analysis of data.

Different ways to draw chart

We can draw a Bar chart using any of the following method. The best way we draw using Rectangle

• Using Lines and Rectangles
• Using Polygon shapes

In this topic we will see by using Rectangle

Drawing Bar chart using Rectangle

Java graphics class have fillRect() method to draw filled rectangle on window.

Example

import java.awt.*;
import java.applet.*;
/* <applet code="DrawBarChart.class" width=300 height=300>
</applet> */

public class DrawBarChart extends Applet
{	
	int values[]={100,150,110,170};
	
	public void paint(Graphics g)
	{
		for(int i=0;i &Lt 4;i++)
		{
			g.setColor(Color.blue);
			g.drawString(Integer.toString(values[i]),20, i*50+30);
			g.fillRect(50,i*50+10, values[i], 40);
		}
	}
}

Output

Drawing Line Graphics

Applets can draw line graphs to show relationships graphically between two values.

Consider following table of x,y values.

Program

import java.awt.*;
import java.applet.*;
/* <applet code="LineGraphics.class" width=600 height=600>
</applet> */

public class LineGraphics extends Applet
{	
	int x[]={0,60,120,180,240,300,360,400};
	int y[]={0,120,180,260,340,340,300,180};
	int points = x.length;
	
	public void paint(Graphics g)
	{
		g.setColor(Color.red);
		g.drawPolygon(x,y,points);
	}
}

Output