Set and Map are two important interfaces of Java. Both are found in the collection framework. Moreover, Set and Map interfaces can be used to store a collection of objects in the form of a single unit. However, the two are not the same and share several differences, and the usage of the two differs as well.
Map vs Set
The main difference between Map and Set is that Map is a mapping interface that connects Keys with the values, but Set is the type of interface that collects unique elements, and it can not carry any duplicate element. Therefore, only one null value can be present in Set, but Map can have more than one null value.
The Map is an interface and part of the Collection interface. As the name implies, it maps the connection between unique keys to the values. In one key, the same values can be repeated, but the same keys can not have a place in Map.
Set is also an interface of the Collection. No duplicate values can take place in this. Even the null value can not be more than one. The mathematical Sets can be generated in this. Set is capable of being traversed.
Comparison Table Between Map and Set
| Parameters of Comparison | Map | Set |
| Definition | It is an interface that is responsible for mapping unique keys to the values. | It is an interface that comes under the Collection interface and it is not capable of carrying duplicate elements. |
| Relation with Collection interface | It is a separate independent interface. | Set is responsible for extending the collection interface. |
| Purpose | The function of Map is to connect between key and value. | The function of Set is to store unique values. |
| Null value | The Map can have as many null values as possible. | At most Set can have one null value. |
| Usage | To store the data in the form of a key or value one should utilize Map. | To create a collection of unique components Set should be used. |
What is Map?
In Java, a Collection interface can be found, and in this, one of the important interfaces is Map. If one wants to use Map, then he/she needs to extend the Collection interface. The Map can store objects as a single unit. The objects are stored in a key-value pair.
It is called Map because it maps the connection between key and value. The keys collected by Map are unique. A key can have the same values, but two keys have to be different. They can not be identical. As all the values are different in a key, one can access the values easily just by using the key.
Any element can be updated or even deleted with the use of Map. The Map is further divided into three classes, TreeMap, LinkedHashMap, and HashMap. A Map is not compatible to be traversed, but if you need to do so, then Map should get converted into Set first.
What is Set?
The Set is an interface that is brought by the Java.util package. The extension of the collection interface can successfully implant this interface. If one has the purpose of designing the mathematical Set, then in Java, Set should get chosen by you. Same elements can not be put in this interface, and thus even the null value can not be entered more than once.
The insertion order can not be maintained by Set. This is due to the reason that it encompasses all the present elements in a sorted way. Iterate, the process that induces a sequence of outcomes, can get done easily if we use the elements of Set. Keys like keyset() and entry set() should get used in it to do the work.
Even though insertion order is not followed in this interface, some classes of it, such as LinkedHashSet, designs the lists in the insertion order. Set orders lists and sorts data. To insert an element, the method “treeset” should be used.
Main Differences Between Map and Set
- The Map is an interface that is responsible for unique mapping keys to the values, whereas Set is an interface that comes under the Collection components and it is not capable of carrying duplicate elements.
- The Map is a separate independent interface, but Set is a part of the collection interface and accountable for the extension of it.
- The null value can be as many as needed in Map, but on the contrary, Set can have one null value at maximum.
- The function of Map is to connect between key and value while Set is given the purpose of storing unique values.
- If you intend to store the data in the form of a key or value, then Map is your option to choose. Set, on the other hand, should be chosen to create a collection of unique components.
Conclusion
Java, the programming language, offers collections for storing data. The base interface that plays a part in carrying out collections in Java is known as Collection. Various interfaces can extend this Collection, and Set is one of those. The Map is also a part of the Collection, although it can not extend it. Both catalogue multiple elements in a single unit form and also perform sorting, searching, inserting as well as deleting. The Set comes under Collection, it is a subtype of it, but Map is separate and not a subtype of it. Set and Map do not operate as each other’s opponents.
The function of the two does not have many similarities as Map attaches values with the keys but Set only stores data that are unique. If duplicate values are unwanted in your database, then Set will suit your purpose, while if you want your keys and values mapped so that they are easily searchable, then Map has such methods to do so.
References
- https://www.aaai.org/ocs/index.php/KR/KR12/paper/viewPaper/4520
- https://dl.acm.org/doi/abs/10.1145/2676726.2676982