In Java programming, a LinkedHashSet is a type of set that stores elements in a specific order, which is the order in which they were added to the set. It is similar to a HashSet, but it also maintains a doubly-linked list that keeps track of the order of the elements.
Let's take an example of a grocery list. Imagine you have a list of items to buy at the store, and you want to make sure that you buy them in the same order that they are listed. A LinkedHashSet can help you with this task.
Here's the basic syntax for creating a LinkedHashSet:
LinkedHashSet<String> hs = new LinkedHashSet<String>();
It works just like a regular HashSet, which means it only stores unique elements. When you add an element to the set using the "add" method, it will maintain the order of the elements.
Here are some examples of how to use a LinkedHashSet:
Example 1:
In this example, we create a LinkedHashSet and add some numbers to it. Then we loop through the set and print out the numbers. Since we added the numbers in a specific order, the LinkedHashSet will maintain that order when we loop through it.
Output: 10 20 30
Example 2:
In this example, we add some numbers to the LinkedHashSet, including a duplicate number. When we print out the set, we can see that it only contains unique numbers, and it maintains the order of the elements.
Output: 10 20 30
Example 3:
In this example, we add some numbers to the LinkedHashSet and then remove one of them. When we print out the set, we can see that the order is maintained and the removed element is no longer present in the set.
Output: [20, 30, 10]
The LinkedHashSet has some important functions that can help us work with the set:
- add(): adds an element to the set if it is not already present.
- contains(): checks if an element is present in the set.
- remove(): removes an element from the set.
- size(): returns the number of elements in the set.
- isEmpty(): checks if the set is empty.
All of these functions have a time complexity of O(1), which means they are very fast and efficient.
It is important to note that maintaining the order of elements in a LinkedHashSet requires additional CPU cycles and memory, so it may not be the best choice for very large sets or sets where the order of elements is not important. In those cases, a regular HashSet may be a better option.