[Javase] Collection frame (HashSet)

Set: Elements are unordered, non-repeatable

Haseset: The underlying data structure is a hash table

Define a class of Demo

Get The demo object,System.out.println (demo), print the demo object,[email Protected]

The Demo object is stored in memory in the hash table, and it is sorted by hash value, so it is unordered

ImportJava.util.HashSet;classdemo{} Public classHashsetdemo {/**     * @paramargs*/     Public Static voidMain (string[] args) {Demo demo1=NewDemo (); Demo Demo2=NewDemo ();        System.out.println (DEMO1);        System.out.println (DEMO2); HashSet Set=NewHashSet ();        Set.add (DEMO1);        Set.add (DEMO2);    SYSTEM.OUT.PRINTLN (set); }}

Results:

[Email protected]

[Email protected]

[[Email protected], [email protected]]

Define a class of Demo

Override the hashcode () method to return a fixed number, for example: $, Print object display,[email protected]

Get multiple objects, hash values are the same, at this point in haseset , using the equals () method, determine whether the same object, if not the same object, will be deferred storage

ImportJava.util.HashSet;classdemo{@Override Public inthashcode () {return90; } @Override Public Booleanequals (Object obj) {System.out.println ("Call here to determine if the same object"); return Super. Equals (obj); }} Public classHashsetdemo {/**     * @paramargs*/     Public Static voidMain (string[] args) {Demo demo1=NewDemo (); Demo Demo2=NewDemo ();        System.out.println (DEMO1);        System.out.println (DEMO2); HashSet Set=NewHashSet ();        Set.add (DEMO1);        Set.add (DEMO2);    SYSTEM.OUT.PRINTLN (set); }}

Results:

[Email protected]

[Email protected]

Called here to determine whether the same object

[[Email protected], [email protected]]

[Javase] Collection frame (HashSet)