Java Map
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Java Map Interface
The Map interface is a part of the Java Collections Framework and is used to store key-value pairs. Each key must be unique, but values can be duplicated.
A Map is useful when you want to associate a key (like a name or ID) with a value (like an age or description).
Common classes that implement Map:
Tip: Use a Map when you want to associate values with unique keys, like storing user IDs with names.
Common Map Methods
| Method |
Description |
put() |
Adds or updates a key-value pair |
get() |
Returns the value for a given key |
remove() |
Removes the key and its value |
containsKey() |
Checks if the map contains the key |
keySet() |
Returns a set of all keys |
Map vs. Set vs. List
| Feature |
List |
Set |
Map |
| Duplicates allowed? |
Yes |
No |
Keys: No
Values: Yes |
| Stores key-value pairs? |
No |
No |
Yes |
| Maintains order? |
Yes |
No (unless using TreeSet or LinkedHashSet) |
No (unless using TreeMap or LinkedHashMap) |
Next, we'll look at how to use HashMap to store items in key/value pairs.
