Bar Graph using java swings

Hello friends.
I am new to java swings please help me. I need a program for drawing Bar graph ( like x and y axis) . It should be changing with change in x and y values continuously. and graph for 3 name consider A ,B and C, for which there should be a bar which shows percentage . with less percentage as green and high percentage as red. for example it can like 3 A , B and C machines for which the bar graph act as heat indicator. the green is for low temp and red for high temp. please help me with java swing codes.
thank you