java - How to get more search data using binary search? -

java - How to get more search data using binary search? -

first of apologize english language , first time asking on stackoverflow if miss please point out.

so i'm new java , trying out binary search help friend. code display product info 1 time searched product id. manage create homecoming index number id found problem when set in multiple same id show 1 data. want programme show index id-12 found.

import java.util.arraylist; import java.util.collections; import java.util.comparator; import java.util.list; public class mylistbinarysearch { public static void main(string a[]){ list<emp> emplist = new arraylist<emp>(); emplist.add(new emp(12,"apple,50,10-5-2014")); emplist.add(new emp(12,"apple,50,5-5-2014")); emplist.add(new emp(124,"apple,50,2-5-2014")); emplist.add(new emp(302,"apple,50,2-5-2014")); emplist.add(new emp(12,"apple,50,2-5-2014")); emp searchkey = new emp(12,"string"); int index = collections.binarysearch(emplist, searchkey, new empcomp()); system.out.println("index of searched key: "+index); } } class empcomp implements comparator<emp>{ public int compare(emp e1, emp e2) { if(e1.getempid() == e2.getempid()){ homecoming 0; } else { homecoming -1; } } } class emp { private int empid; private string empinfo; public emp(int id, string info){ this.empid = id; this.empinfo = info; } public int getempid() { homecoming empid; } public void setempid(int empid) { this.empid = empid; } public string getempinfo() { homecoming empinfo; } public void setempinfo(string empinfo) { this.empinfo = empinfo; } @override public string tostring(){ homecoming empid+" : "+empinfo; } }

the out "index of searched key: 2" want display index search key found. how do ? need loop ?

you have 2 problems:

your comparator should homecoming greater 0 when current element greater compared element, 0 when elements equals , less 0 when current element less compared element. current implementation doesn't cover this. binary search works on sorted arrays/lists only. list not sorted id.

after fixing issues, utilize binary search. after retrieving index element 12, can search around element retrieve elements have same id.

this thought how implement it:

int index = collections.binarysearch(emplist, searchkey, new empcomp()); list<emp> empswithid12 = new arraylist<emp>(); (int = index - 1; >= 0; i--) { emp emp = emplist.get(i); if (emp.getid() == 12) { empswithid12.add(emp); } else { break; } } collections.reverse(empswithid12); (int = index; < emplist.size(); i++) { emp emp = emplist.get(i); if (emp.getid() == 12) { empswithid12.add(emp); } else { break; } }

note thought above can improved moving logic method.

java arrays search indexing