Determine if the elements in the set are duplicated, = =, equals, Hashcode method research-code Demo

Sitebean site1 =NewSitebean ("http://www.yjbys.com/", "" "); Sitebean Site2=NewSitebean ("http://www.yjbys.com/", "" "); Set<SiteBean> Aaset =NewHashset<>();        Aaset.add (SITE1);        Aaset.add (SITE2); System.out.println (Site1==site2);        System.out.println (Site1.equals (site2)); System.out.println (Site1.hashcode ()==Site2.hashcode ()); Sitebean Site3=NewSitebean ("Http://www.yjby1s.com/11", "" "); Sitebean Site4=NewSitebean ("Http://www.yjby1s.com/11", "" ");        Aaset.add (Site3); Aaset.add (site4);

Sitebean overrides the Hashcode and Equals methods with the following code://The comparison is the domain name@Override Public inthashcode () {returnSiteurl.hashcode (); }    //The comparison is the domain name@Override Public Booleanequals (Object obj) {if(obj = =NULL) {            return false; }        if(GetClass ()! =Obj.getclass ()) {            return false; }        FinalSitebean Sitebean =(Sitebean) obj; returnobjects.equals (SiteURL, Sitebean.siteurl); }

The output is as follows:

false true true
and the number of elements in set is 2.

The internal implementation of the set is actually a map, and the Hashcode method is called when the key of the map is processed, the code is as follows

Static Final int Hash (Object key) {        int  h;         return null) ? 0: (H = key.hashcode ()) ^ (h >>>);    }

After calling the Hashcode method method, the Equals method is called, so the element repeatability of set is judged by equals.

The following attempt does not override the Hashcode method:

Output:

false true false
and the number of elements in set is 4.

The following attempt does not override the Hashcode and Equals methods:

Output:

Falsefalse
and the number of elements in set is 4.

Ouyen Rights

Reprint Annotated: http://www.cnblogs.com/langtianya/p/4421582.html

Determine if the elements in the set are duplicated, = =, equals, Hashcode method research-code Demo