Exercises: Simple Methods

Please define, for each exercise:

parameters types and names, if any
return value type, if any
the implementation, the body of the method

Methods should do only one thing.

The main method is where you should ask users for values, call the single methods of this exercise, and print results.

The methods should not have any hardcoded number or string.

addNumbers

Write a method public static int addNumbers(int max) to add together all numbers from 1 to max. Please use a for loop to sum up all numbers.

E.g.:

For max = 5 the method shall return 15, because 1 + 2 + 3 + 4 + 5 are equal to 15

multiplyNumbers

Write a method public static int multiplyNumbers(int max) which multiplies all numbers from 1 to max. Please use a for loop to multiply all numbers.

E.g.:

For max = 5 the method shall return 120, because 1 * 2 * 3 * 4 * 5 gives 120.

findClosestDivisbleNumber

Write a method public static int findClosestDivisibleNumber(int number, int divisor) which finds the number which is divisible by another number and which is closest to another given number.

E.g.:

Number given is 13. Given divisor is 5. Result shall be 10.

areEqual

Write a method that, given four int, returns if they’re all equal, so if they all have the same value.

Do the exercise again with String.

greatest

Write a method that, given three int, returns the greater of the three. The method must work also in corner cases, like when all the numbers are the same and when two numbers are the same.

EXTRA: extend the exercise to 4 or 5 numbers.

powerOf

Write a method that calculates the power of a number. The base should be of type double, the exponent should be of type int.

Examples:

powerOf(4, 2) = 4 × 4 (two times)
powerOf(3, 4) = 3 × 3 × 3 × 3 (four times)
powerOf(7.123, 3) = 7.123 × 7.123 × 7.123 (three times)
powerOf(-3.5, 2) = -3.5 × -3.5 (two times)
powerOf(10, 1) = 10 (one time)
powerOf(99, 0) = 1 (zero times)

NOTE: you may find that a method like this already exist. It is called Math.pow(). Since this is exercise, please don’t use it and try to implement the exercise manually with a for loop.

areaOfCircle

Write a method that calculates the area of a circle, given its radius. Search on Google, if you need the formula.

Use the double type, not int, for both parameter and return value.

You’ll need the constant π, the Greek Pi, that is approximately 3.14. It’s better to use the Java constant Math.PI instead of typing directly 3.14 in the code.

circleCircumference

Having done the areaOfCircle method it should be fairly simple to write a method that calculates the circumference of a circle, given its radius.

hypotenuse (Pythagoras’ theorem)

Write a method that calculates the hypotenuse of a right triangle, given the length of its sides. The hypotenuse is the side opposite the right angle. For more information, see https://en.wikipedia.org/wiki/Pythagorean_theorem. Search on Google, if you need the formula.

Use the double type, not int, for both parameters and return value.

You’ll need to calculate the square root of a number, use the method Math.sqrt() for that.

Number Pyramid

Write a method like public static void printPyramid(int height) that prints such pyramid pattern (s. below) for height rows. Every row grows up from 1 to the row number and back to one. It will help to write a method like public static void printPyramidRow(int row, int maxHeight), which prints one row of the pyramid.

Example for height = 5:

HINT: print some spaces, then increasing numbers, then decreasing numbers.