Sets

• A set is a collection of:

  • unordered elements
  • unique elements

• Doesn’t know where they are, just knows that they exist there.

• No performance decrease when sample size increase as opposed to an Array

When To Use:

• don’t care how many times something exists or where it exists

• Use sets over arrays because it is faster and simpler to performs operations on it

• A set is a collection of:

  • unordered elements
  • unique elements

• Doesn’t know where they are, just knows that they exist there.

• No performance decrease when sample size increase as opposed to an Array

Operations You Can Perform On A Set:

• .add()

  • only appends to the set if the element is not present
  • if it is present you get a boolean return type back of false

• .addAll(collection)

  • add to my set all the elements from specified collection

• .clear()

  • removes all the elements from the set

• .hashCode()

  • give the hashCode of the instance of my set

• .isEmpty()

  • checking to see if my set is empty or not

• .remove()

  • throw out a specific item from my set

• .size()

  • output to me the size of my set

• .toArray()

  • generate an Array for me of all the items within my set

There are three types of sets:

• HashSet: no particular order
  • insertion: O(1)
  • removal: O(1)
  • contains: O(1)
• LinkedHashSet: insertion order
  • insertion: O(1)
  • removal: O(1)
  • contains: O(1)
• TreeSet: sorted order
  • insertion: O(n*logn)
  • removal: O(n*logn)
  • contains: O(n*logn)