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Before we start, did you try solving the workbook yourself?

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If not, please click the link in the resources folder and follow the instructions for this workbook.

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Welcome to Work Book 4.5.

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In this workbook, we're going to print the areas for a square rectangle, triangle and circle and task

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one.

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We have to define all the functions been defined.

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We just have to write the logic for it first.

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Inside the function, we check if the side that was passed in is negative, in which case we need to

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print impossible and terminate the Java program.

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We cannot let them proceed.

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So we'll say if side is smaller than zero.

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Then print error and possible.

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And then terminate the runtime system Exit zero OC.

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But otherwise, if the side that they pass in is good, then we're going to calculate the area of the

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square and return it.

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Now, if you want to do something to the power of something else, you can use the math power function.

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Power is a built in Java function that we can get from the math class and it expects to values.

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The first value is the base.

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The second value is the exponent.

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Our base is side and the exponent is going to be two.

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So this function is going to return the double result from doing side to the power of two.

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And that's all.

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All right.

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And now the remaining functions are going to follow a very similar logic.

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So I'll give you the chance to pause the video and try to complete them on your own.

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All right.

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Welcome back.

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So this one is fairly easy.

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First, you check if the length or width are negative.

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If they are, you say not possible and terminate the application.

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But if this doesn't execute, then runtime will keep going, in which case you're going to return the

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area of a rectangle which is length times width.

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I will delete the dot comment.

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And moving on to task number three, which was to calculate the area of a triangle.

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Again, we do a safeguard.

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If they pass in an invalid base or height, we terminate the application.

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Otherwise, runtime continues and we return the area of a triangle.

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And now in task number four, your function needs to return the area of a circle.

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First, you check if the radius is negative.

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If that happens to be the case, we print not possible and terminate the application.

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Otherwise we return pi.

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So pi is a field from the math class that equals 3.14159, etc. It is better practice to reference pie

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from the math class as opposed to actually writing 3.1 for yourself.

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And then all we're doing is multiplying that by radius to the power of two as you were instructed to

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do so inside of learn the part.

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The area of a circle is equal to pi times radius to the power of two.

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And that is all.

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All right.

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Task number five is to call the area functions.

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So here we'll say, Well, you know what?

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Let's just uncomment these here.

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We can calculate the area of a square.

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With a side of two.

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Here we calculate the area of a rectangle with a length of one and a width of two.

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Here we calculate the area of a triangle.

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With a base of one and a height of two.

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And here we calculate the area of a circle with a radius of what was it again?

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A radius of two.

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All right.

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That was task number five.

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Task number six was to define a function that prints every single area.

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So the function is going to be public static.

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As always, it's going to be void because no return type was specified in the doc comment and we're

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not returning anything because all we'll be doing is printing a bunch of areas.

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It's going to receive four parameters.

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Double square.

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Double rectangle.

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Double triangle.

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And double circle.

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So when called this function expects to receive four values, we're going to print all of these values

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in accordance with what we have specified over here.

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Looking good.

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Deleting this.

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And I'm pretty sure we're all done.

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The next step is to call a function that prints all the areas, and that function is print areas.

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It's time to run the code.

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But as always, I would prefer to visualize the runtime.

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So I will place breakpoints over here and that will be all.

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Let us now visualize it.

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Dismissing this debug console.

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Minimizing this window.

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So first, we're calling the function area square, passing in a side of to the parameter side stores.

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The value that was passed in two is not smaller than zero.

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So this gets skipped and two to the power of two is going to return for.

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The square variable equals the return value of four.

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Beautiful.

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And now we're calling area rectangle, passing in two values.

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The first parameter store is the first value, lowest pass, then the second parameter store is the

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second value that was passed in.

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None of the parameters are less than zero.

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So this statement is going to get skipped and here it returns the area of a rectangle length times width.

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And now we're setting the rectangle variable equal to the return value of two.

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All right.

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Now, we've calculated two areas, one for the square, one for the rectangle.

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Now we're calling a function that calculates the area of a triangle passing in two values.

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The first parameter store is the first value that was passed in.

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The second parameter stores.

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The second value that was passed in.

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Here we're checking if either value is less than zero.

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That is not the case.

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So this if statement gets skipped and here we return the area of a triangle.

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The function call retains this return value.

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And here we set our variable equal to an area of one.

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All right, Now we've got three areas.

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Stepping inside the function area circle.

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Here.

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We check if the radius that was passed in is smaller than zero.

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That is not the case.

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So the if statement gets skipped.

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And now here we're doing 3.1, four times two to the power of two, which is going to result in a return

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value of 12.56.

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And then we're setting the variable equal to it.

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All right.

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And then print areas is just going to print all of these areas.

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Beautiful.

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This was the last workbook for the function section, and I really hope you've been enjoying these breakpoint

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sessions.