The Java Boutique: Java Tutorial: Java by Example: Functions and Arrays

Tutorials : Java by Example : Section 4 :

Section Four Contents

Functions and Arrays

Loops, Advanced Color Functions

Here it is demonstrated how to use loops for a repeating task, here in order to draw graphics primitives several times.
For our loop we use the "for-loop" - the syntax is:

for (initialization; test-expression; update-expression)

body

Just study the code and you will see what is meant. Of the three loop variants (for, while, do-while) this is the one you will need most and it's the shortest and most elegant. The variable for the incrementation (in most cases by convention called i / j / k - or x / y, if you need it for coordinates) can be defined inside the head of the loop, if you need it only once. If you need it several times inside the same method, you should define a local variable in your method: int i;.

//Sourcecode

import java.awt.*; import java.applet.*; public class Project13 extends Applet { public void paint (Graphics g) { int x; int rightBorder=220; //paints a row of red Squares g.setColor(Color.red); for(x=0;x<rightBorder;x+=20) g.fillRect(x,20,18,18); //many (hollow) blue Circles g.setColor(Color.blue); for(x=0;x<rightBorder;x+=30) g.drawOval(x,80,28,28); //lots of black lines g.setColor(Color.black); for(x=0;x<rightBorder;x+=5) g.drawLine(x,140,x,280); //a vertical row of yellow squares with round corners g.setColor(Color.yellow); for(int y=20;y<280;y+=30) g.fillRoundRect(250,y,40,25,15,15); } }

Applet Index
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The Java Source
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