HashMap should be unsorted but still sorts according to key
data-structures, hashmap, java, sorting
Solution
It's a coincidence (not really, rather it has to do with the hashing algorithm).
Try adding
newHashMap.put(-5, "Fifth");
as last.
Output will be
Key: 0
Value: Second
Key: 1
Value: Fourth
Key: 2
Value: First
Key: 3
Value: Third
Key: -5
Value: Fifth
The javadoc specifically says
This class makes no guarantees as to the order of the map; in particular, it does not guarantee that the order will remain constant over time.
Problem
According to these: - http://docs.oracle.com/javase/6/docs/api/java/util/HashMap.html - Difference between HashMap, LinkedHashMap and TreeMap - java beginner : How key gets sorted in hashmaps? The `HashMap` in `Java` should be unsorted but it is being sorted with respect to `Key`. I experienced this as a problem because I needed inserted-order data. So, I used `LinkedHashMap` instead. But still I am confused why the `HashMap` sorted it. Can anyone explain it? I did a simple example to view the sort. ``` public static void main(String[] args) { HashMap<Integer, String> newHashMap = new HashMap<Integer, String>(); newHashMap.put(2, "First"); newHashMap.put(0, "Second"); newHashMap.put(3, "Third"); newHashMap.put(1, "Fourth"); Iterator<Entry<Integer, String>> iterator = newHashMap.entrySet() .iterator(); while (iterator.hasNext()) { Map.Entry<Integer, String> entry = iterator.next(); System.out.println("Key: " + entry.getKey()); System.out.println("Value: " + entry.getValue()); iterator.remove(); } } ``` Result: ``` Key: 0 Value: Second Key: 1 Value: Fourth Key: 2 Value: First Key: 3 Value: Third ``` Edit: I tried to insert 50 random numbers using `Random` of `Java` and I found some data unsorted. But, it still manages to sort most of the integers. Random results: ``` ... Key: 36 Value: random Key: 43 Value: random Key: 47 Value: random Key: 44 Value: random Key: 45 Value: random ... ```