Java: Hashtable stores multiple items with same hash in one bucket -

Java: Hashtable stores multiple items with same hash in one bucket -

problem description

while reading oracle documentation hashtable found "in case of "hash collision", single bucket stores multiple entries, must searched sequentially", seek find method homecoming me items sequentially, if have 2 items same hash, can't find in documentation. in order reproduce situation seek write simple code, can find below.

oracle documentation hashtable

an instance of hashtable has 2 parameters impact performance: initial capacity , load factor. capacity number of buckets in hash table, , initial capacity capacity @ time hash table created. note hash table open: in case of "hash collision", single bucket stores multiple entries, must searched sequentially. load factor measure of how total hash table allowed before capacity automatically increased. initial capacity , load factor parameters simply hints implementation. exact details when , whether rehash method invoked implementation-dependent.

simple code class key { public final int mid; public key(int id) { mid = id; } @override public int hashcode() { if(mid == 1 || mid == 2) { system.out.println("have same hashcode()"); homecoming 5673654; } homecoming super.hashcode(); } }; public class hashtabletest { public static void main(string... args) { hashtable<key, string> dict = new hashtable<key, string>(); dict.put(new key(1), "one"); dict.put(new key(2), "two"); system.out.println(dict.size()); // prints 2 system.out.println(dict.get(new key(1))); // prints null } };

in code above seek add together hashtable 2 items have same hashcode (anyway think have :) ), create key class , override it's hashcode method, useless can't item hashtable , think items not added sequentially.

questions how can simulate situation of stores multiple entries in 1 bucket? (in order more understand how work) how can access items in hashtable stored sequentially?

the hashtable (and hashmap) implement collision resolution storing multiple keys map same bucket number.

however, need override equals method in key. hashtable (or hashmap) find key exists in map, hash codes used find bucket, equals used distinguish distinct keys in same bucket. because aren't overriding equals, key inherits equals object, determines if 2 objects same object, not whether contents equal.

the equals method class object implements discriminating possible equivalence relation on objects; is, non-null reference values x , y, method returns true if , if x , y refer same object (x == y has value true).

note necessary override hashcode method whenever method overridden, maintain general contract hashcode method, states equal objects must have equal hash codes.

java hashtable