The TreeMap is used to store <key, value> pairs. It is sorted according to the natural ordering of its keys, or by a Comparator provided at map creation time, depending on which constructor is used.
A few important facts about TreeMap are as follows:
- It is not synchronized.
- It does not allow null keys, but values can be null.
Hierarchy of TreeMap class
It inherits methods from AbstractMap and implements Serializable, Clonable, and NavigatableMap interfaces.
Source code of Item.java
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package com.t4b.test;
public class Item {
String name;
int id;
double price;
public Item(String name, int id, double price) {
super();
this.name = name;
this.id = id;
this.price = price;
}
@Override
public String toString() {
return "Item [name=" + name + ", id=" + id + ", price=" + price + "]";
}
}
Source code of TestMain.java
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package com.t4b.test;
import java.util.TreeMap;
import java.util.Map;
public class TestMain {
public static void main(String[] args) {
TreeMap<Integer, Item> map = new TreeMap<Integer, Item>();
map.put(1, new Item("Apple", 1, 150.0));
map.put(2, new Item("Grape", 2, 250.0));
map.put(3, new Item("Mango", 3, 10));
map.put(2, new Item("Pine Apple", 4, 100));
for (Map.Entry item : map.entrySet()) {
System.out.println(item.getKey() + " : " + item.getValue());
}
}
}
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