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Returning values

So far, every method you have defined has had the return type of void - in essence, the methods return nothing. However in many cases you may want the method to return a value in the form of an int, double, String, boolean or any other data type.

Here's an example:

1public static int divideBy4(int num) {
2    num = num/4;
3    return num;

In the example above, note that the return type has changed from void to int. Because it is not void anymore, this means that we're specifying the method to return something, and we've specified it to return an integer value.

1public static void main(String[] args) {
2    int division = divideBy4(5);

Ex 1

Write a method which calculates and returns the curved surface area of a cylinder.

(Hint: You will need to import the maths API in order to use pi: import java.lang.Math; in order to use pi you will have to call it with Math.PI)

Ex 2

Write an accompanying method which calculates and returns the volume of a cylinder.

Ex 3

Write a method which converts and returns a given angle in degrees to radians. The write a method that converts radians to degrees.

(Hint: Research what radians are and how to convert to them. Also, think carefully: do we want to be using variables of type int or type double?)

Ex 4

Write another method which calculates the hypotenuse of a right-angled triangle.

Ex 5

Write two methods which calculate and return the curve surface area and volume of a cone.

Ex 6

Finally, write another two more methods which calculate and return the surface area and volume of a sphere.


So far you have learnt that parameters can be declared between the brackets (__) in a method header:

1public static void divideBy2(double a)

The method body could be something like:

2  a = a/2;

Writing a = a/2 is OK because we've already declared it as a parameter of type double in the parameter list. Note that a only exists within the method body, due to its scope. Essentially this means is that a can only be used within the divideBy2 method; if you try to do something like a = ... somewhere else in the program, it won't work.

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