Exploring The New Method Added To Map In Java 9

Introduction

Java 9 has brought along several changes, and one of the most notable ones is the addition of a new method to the Map interface. This new method is called 'computeIfAbsent', and it allows for a more streamlined and efficient way of working with maps. In this article, we will take a closer look at this new method and discuss its benefits and how it works.

What is the 'computeIfAbsent' method?

The 'computeIfAbsent' method is a new addition to the Map interface in Java 9. It is used to compute a value for a given key if it is not already present in the map. This method takes two parameters: the key for which the value needs to be computed and a function that will compute the value if it is not already present in the map.

How does the 'computeIfAbsent' method work?

The 'computeIfAbsent' method works by first checking if the map contains the key for which the value needs to be computed. If the key is not present, the method will call the provided function to compute the value. The computed value will then be added to the map with the provided key. If the key is already present, the method will simply return the existing value.

What are the benefits of using the 'computeIfAbsent' method?

The 'computeIfAbsent' method provides several benefits. Firstly, it allows for a more streamlined and efficient way of working with maps. Instead of having to write complex code to check if a key is present in the map and then compute the value if it is not, the 'computeIfAbsent' method handles all of this for you in a single line of code.

Secondly, the 'computeIfAbsent' method helps to reduce the amount of boilerplate code that is required when working with maps. This makes the code more readable and easier to maintain.

Examples of using the 'computeIfAbsent' method

Let's take a look at some examples of using the 'computeIfAbsent' method:

Example 1:

Suppose we have a map that contains the following key-value pairs:

Map map = new HashMap<>(); map.put("apple", 1); map.put("banana", 2); map.put("orange", 3); 

If we want to compute the value for a key that is not present in the map, we can use the 'computeIfAbsent' method as follows:

map.computeIfAbsent("grape", k -> 4); 

This will add a new key-value pair to the map with the key "grape" and the value 4.

Example 2:

Suppose we have a map that contains the following key-value pairs:

Map> map = new HashMap<>(); map.put("fruits", Arrays.asList("apple", "banana", "orange")); map.put("vegetables", Arrays.asList("carrot", "potato")); 

If we want to compute the value for a key that is not present in the map and the value is a list, we can use the 'computeIfAbsent' method as follows:

map.computeIfAbsent("meat", k -> new ArrayList<>()); 

This will add a new key-value pair to the map with the key "meat" and an empty list as the value.

Conclusion

The 'computeIfAbsent' method is a useful addition to the Map interface in Java 9. It provides a more streamlined and efficient way of working with maps and helps to reduce the amount of boilerplate code that is required. By using this method, you can write cleaner, more readable code that is easier to maintain.

Question & Answer

Q: What is the purpose of the 'computeIfAbsent' method?

A: The 'computeIfAbsent' method is used to compute a value for a given key if it is not already present in the map.

Q: What are the benefits of using the 'computeIfAbsent' method?

A: The 'computeIfAbsent' method provides several benefits. Firstly, it allows for a more streamlined and efficient way of working with maps. Secondly, it helps to reduce the amount of boilerplate code that is required when working with maps.

Q: Can the 'computeIfAbsent' method be used for maps with values that are not of type 'Integer'?

A: Yes, the 'computeIfAbsent' method can be used for maps with values of any type.