TreeMap is a class which is available in java.util package. The TreeMap is a class of the Java collections framework provides the functionality of tree data structure. In Java TreeMap, elements are stored in key/value pairs. Keys are unique values associated with individual values. TreeMap cannot contains duplicate keys.
TreeMap Syntax:
TreeMap<K, V> numbers = new TreeMap<>();
TreeMap<String, Integer> numbers = new TreeMap<>();
| Method Name | Description |
|---|---|
| put() | inserts the specified key/value mapping to the map. |
| putAll() | inserts all the entries from the specified map to this map. |
| putIfAbsent() | inserts the specified key/value mapping to the map if the specified key is not present in the map. |
| entrySet() | returns a set of all the key/values mapping (entry) of a treemap. |
| keySet() | returns a set of all the keys of the map. |
| values() | returns a set of all the values of the map. |
| get() | Returns the value associated with the specified key. Returns null if the key is not found. |
| getOrDefault() | Returns the value associated with the specified key. Returns the specified default value if the key is not found. |
| remove(key) | returns and removes the entry associated with the specified key from the TreeMap. |
| remove(key, value) | removes the entry from the map only if the specified key is associated with the specified value and returns a boolean value. |
| replace(key, value) | replaces the value mapped by the specified key with the new value. |
| replace(key, old, new) | replaces the old value with the new value only if the old value is already associated with the specified key. |
| replaceAll(function) | replaces each value of the map with the result of the specified function. |
| clear() | removes all the entries from the map. |
| containsKey() | checks if the map contains the specified key and returns a boolean value. |
| containsValue() | checks if the map contains the specified value and returns a boolean value. |
| size() | returns the size of the map. |
| isEmpty() | checks if the map is empty and returns a boolean value. |
import java.util.TreeMap;
class Main {
public static void main(String[] args) {
// Creating TreeMap of even numbers
TreeMap<String, Integer> evenNumbers = new TreeMap<>();
// Using put()
evenNumbers.put("Two", 2);
evenNumbers.put("Four", 4);
// Using putIfAbsent()
evenNumbers.putIfAbsent("Six", 6);
System.out.println("TreeMap of even numbers: " + evenNumbers);
//Creating TreeMap of numbers
TreeMap<String, Integer> numbers = new TreeMap<>();
numbers.put("One", 1);
// Using putAll()
numbers.putAll(evenNumbers);
System.out.println("TreeMap of numbers: " + numbers);
}
}
import java.util.TreeMap;
class Main {
public static void main(String[] args) {
TreeMap<String, Integer> numbers = new TreeMap<>();
numbers.put("One", 1);
numbers.put("Two", 2);
numbers.put("Three", 3);
System.out.println("TreeMap: " + numbers);
// Using entrySet()
System.out.println("Key/Value mappings: " + numbers.entrySet());
// Using keySet()
System.out.println("Keys: " + numbers.keySet());
// Using values()
System.out.println("Values: " + numbers.values());
// Using get()
int value1 = numbers.get("Three");
System.out.println("Using get(): " + value1);
// Using getOrDefault()
int value2 = numbers.getOrDefault("Five", 5);
System.out.println("Using getOrDefault(): " + value2);
}
}
import java.util.TreeMap;
class Main {
public static void main(String[] args) {
TreeMap<String, Integer> numbers = new TreeMap<>();
numbers.put("One", 1);
numbers.put("Two", 2);
numbers.put("Three", 3);
System.out.println("TreeMap: " + numbers);
// remove method with single parameter
int value = numbers.remove("Two");
System.out.println("Removed value: " + value);
// remove method with two parameters
boolean result = numbers.remove("Three", 3);
System.out.println("Is the entry {Three=3} removed? " + result);
System.out.println("Updated TreeMap: " + numbers);
}
}
import java.util.TreeMap;
class Main {
public static void main(String[] args) {
TreeMap<String, Integer> numbers = new TreeMap<>();
numbers.put("First", 1);
numbers.put("Second", 2);
numbers.put("Third", 3);
System.out.println("Original TreeMap: " + numbers);
// Using replace()
numbers.replace("Second", 22);
numbers.replace("Third", 3, 33);
System.out.println("TreeMap using replace: " + numbers);
// Using replaceAll()
numbers.replaceAll((key, oldValue) -> oldValue + 2);
System.out.println("TreeMap using replaceAll: " + numbers);
}
}