When you insert the pair (10, 17) and then (10, 20), there is technically no collision involved. You are just replacing the old value with the new value for a given key 10 (since in both cases, 10 is equal to 10 and also the hash code for 10 is always 10). Collision happens when … Read more
hellow has shown how to get working code, but I want to dive a bit more into why your code does not compile. The code you have proposed cannot be statically verified to be memory safe. It’s entirely possible that your recursive calls attempt to access the same index. Check out this simplified code for … Read more
Under the appropriate assumptions on the hash function being used, we can say that hash table lookups take expected O(1) time (assuming you’re using a standard hashing scheme like linear probing or chained hashing). This means that on average, the amount of work that a hash table does to perform a lookup is at most … Read more
The short answer To find out how large an object is, I would use a profiler. In YourKit, for example, you can search for the object and then get it to calculate its deep size. This will give a you a fair idea of how much memory would be used if the object were stand … Read more
Well if you know the basics behind them, it shouldn’t be too hard. Generally you create an array called “buckets” that contain the key and value, with an optional pointer to create a linked list. When you access the hash table with a key, you process the key with a custom hash function which will … Read more
There are several options: 2 dimensions Map of maps Map<Integer, Map<Integer, V>> map = //… //… map.get(2).get(5); Wrapper key object public class Key { private final int x; private final int y; public Key(int x, int y) { this.x = x; this.y = y; } @Override public boolean equals(Object o) { if (this == o) … Read more
HashSet is a set, e.g. {1,2,3,4,5} HashMap is a key -> value (key to value) map, e.g. {a -> 1, b -> 2, c -> 2, d -> 1} Notice in my example above that in the HashMap there must not be duplicate keys, but it may have duplicate values. In the HashSet, there must … Read more
To answer your question in one sentence: Per default, Maps don’t have a last entry, it’s not part of their contract. And a side note: it’s good practice to code against interfaces, not the implementation classes (see Effective Java by Joshua Bloch, Chapter 8, Item 52: Refer to objects by their interfaces). So your declaration … Read more
Short answer Use a TreeMap. This is precisely what it’s for. If this map is passed to you and you cannot determine the type, then you can do the following: SortedSet<String> keys = new TreeSet<>(map.keySet()); for (String key : keys) { String value = map.get(key); // do something } This will iterate across the map … Read more
Don’t use Properties, which is legacy Divide entries into multiple files Read each file in sequence, load and process using Preferences Example code: package com.mypack.test; import java.io.*; import java.util.*; import java.util.prefs.Preferences; public class PreferencesExample { public static void main(String args[]) throws FileNotFoundException { Preferences ps = Preferences.userNodeForPackage(PreferencesExample.class); // Load file object File fileObj = new … Read more