How To Get Key Value From Map In Java

Table of Contents

Introduction

Java is a versatile programming language that offers a variety of data structures to work with. One such data structure is Map, which is used to store key-value pairs. In this article, we will discuss how to get a key value from Map in Java.

What is a Map in Java?

A Map in Java is an interface that represents a mapping between a key and a value. It is part of the java.util package and is implemented by several classes such as HashMap, TreeMap, and LinkedHashMap.

How to Get Key Value from Map in Java?

To get a value associated with a key in a Map, we can use the get() method. The get() method takes the key as an argument and returns the corresponding value. Here's an example: ``` Map map = new HashMap<>(); map.put("apple", 1); map.put("banana", 2); map.put("orange", 3); int value = map.get("banana"); System.out.println(value); // Output: 2 ``` In the above example, we create a HashMap and add three key-value pairs to it. Then, we use the get() method to retrieve the value associated with the key "banana" and store it in the variable value. Finally, we print the value to the console.

What Happens When the Key is Not Found?

If the key is not found in the Map, the get() method returns null. Therefore, it is important to check whether the returned value is null before using it. Here's an example: ``` Map map = new HashMap<>(); map.put("apple", 1); map.put("banana", 2); map.put("orange", 3); Integer value = map.get("grape"); if (value != null) { System.out.println(value); } else { System.out.println("Key not found"); } ``` In the above example, we try to retrieve the value associated with the key "grape", which is not present in the Map. Therefore, the get() method returns null. We check whether the returned value is null and print "Key not found" to the console.

Conclusion

In this article, we discussed how to get a key value from Map in Java using the get() method. We also discussed what happens when the key is not found in the Map. By using the get() method correctly and checking for null values, we can effectively retrieve values from a Map in Java.

Question & Answer

Q: What is a Map in Java?
A: A Map in Java is an interface that represents a mapping between a key and a value. Q: How do you get a value associated with a key in a Map?
A: To get a value associated with a key in a Map, you can use the get() method. The get() method takes the key as an argument and returns the corresponding value. Q: What happens when the key is not found in the Map?
A: If the key is not found in the Map, the get() method returns null. Therefore, it is important to check whether the returned value is null before using it.