Field Detail

• cache

  ArrayList<Long> cache

  Stores all found amicable numbers.

Constructor Detail

• PE0021

  public PE0021()

  A simple constructor to set number and title.

Method Detail

• prepare

  public void prepare()

  Just initializes the cache as empty memory.

  Specified by:

  prepare in interface Solvable

  Overrides:

  prepare in class Problem

• solve

  public String solve()

  Runs a loop to 10000 and checks if the current number is amicable. A found amicable number is added to final sum.

  Returns:

  the sum of all found amicable numbers

  See Also:

  isAmicable(int)

• isAmicable

  private boolean isAmicable(int num)

  Checks the given number to be a amicable number. Therefore first the cache is asked. If the number could not be found in cache the sum of divisors is calculated.

  Parameters:

  num - the number to be checked

  Returns:

  true if the number is amicable

  See Also:

  Mathe.getSumOfDivisors(long)