Dave Drohan (SETU)

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While Loops

In this step, we will implement the code examples 4.5 and 4.6 from your lectures. We will also do an exercise with a nested while loop.

while Loop

Create a new Processing sketch and call it Example_4_5.

Enter the following code into your sketch:

int yCoordinate = 60;

size(600, 300);
background(102);
fill(255);
noStroke();
int i = 0;

while (i < 4) 
{
    rect(50, yCoordinate, 500, 10);
    yCoordinate = yCoordinate + 20;
    i++;
}

Run your code. This code should draw four white horizontal blocks as shown below:

Save your sketch.

Same loop, but without the yCoordinate variable

In the above sketch, do a Save as… and give it the name Example_4_6.

Make the necessary changes to remove the yCoordinate variable and update the while loop accordingly:

size(600, 300);
background(102);
fill(255);
noStroke();

int i = 60; 
while(i  <= 120)
{
    rect(50, i, 500, 10);
    i += 20;
}

Run it and check that the same output as above is produced.

Save your sketch.

Nested While Loops

Create a new Processing sketch in your workspace and call it lab04_step02.

Enter the following code into your sketchbook:

int i = 0;   
while ( i < 4 ) {
   int j = 0;
   while (j < 4 ) {
      println("The value of i is: " + i + " and j is: " + j);
      j++;
   } 
   i++;
}

Run your code. This code should print out this series of lines to your console:

Look at these lines, in particular, look at the values printed for i and for j. Do you understand the mechanics of how the nested while loop works?

Save your sketch.