How To Use Map In Java

Introduction

What is Map?

Creating a Map

 Map map = new HashMap<>(); 

Adding Elements to Map

 map.put("key1", "value1"); map.put("key2", "value2"); 

Accessing Elements from Map

 String value1 = map.get("key1"); String value2 = map.get("key2"); 

Removing Elements from Map

 map.remove("key1"); 

Iterating over Map

 for(Map.Entry entry : map.entrySet()) { String key = entry.getKey(); String value = entry.getValue(); System.out.println(key + " =" + value); } 

Sorting Map

 Map sortedMap = new TreeMap<>(map); 

Conclusion

Question & Answer

Q: What is Map in Java?

A: Map is an interface in Java that represents a mapping between keys and values. It is implemented by various classes such as HashMap, TreeMap, and LinkedHashMap. Map stores data in the form of key-value pairs.

Q: How do you create a Map in Java?

A: To create a Map in Java, we can use the HashMap class, which is the most commonly used implementation of the Map interface. Here is an example:

 Map map = new HashMap<>(); 

Q: How do you add elements to Map?

A: We can add elements to Map using the put() method. Here is an example:

 map.put("key1", "value1"); map.put("key2", "value2"); 

Q: How do you access elements from Map?

A: We can access elements from Map using the get() method. Here is an example:

 String value1 = map.get("key1"); String value2 = map.get("key2"); 

Q: How do you remove elements from Map?

A: We can remove elements from Map using the remove() method. Here is an example:

 map.remove("key1"); 

Q: How do you iterate over Map?

A: We can iterate over Map using the entrySet() method. Here is an example:

 for(Map.Entry entry : map.entrySet()) { String key = entry.getKey(); String value = entry.getValue(); System.out.println(key + " =" + value); } 

Q: How do you sort Map?

A: We can sort Map by keys or values using the TreeMap class. Here is an example:

 Map sortedMap = new TreeMap<>(map);