Searching Lists of Custom Employee Objects each based on first name and last name in Java -

after doing lots of research on stackoverflow, found solution searching based on 1 attribute using overriding equals() method.

my question is: have list of employee objects containing first name, last name , employee ids.

arraylist.stream().filter() work java 8. need solution can work java 7.

suppose, there 10 employee objects first , last names as:

jam jon1 [note: first name : jam , last name : jon1]

jam jon2

jam jon3

jam jon4

jam jon5

pam jin

pam jin

pam jin

pam jin

pam jin

now, have 1 input i.e. jam.

i want list of employee objects containing jam first name.

now, have input i.e. jin.

i want list of employee objects containing jin last name.

i have 500 employee objects in arraylist.

employee class:

public class employee{   string firstname;   string lastname;      employee(string firstname, string lastname){         this.firstname = firstname;         this.lastname = lastname;     }  }  employee emp1 = new employee("jam","jon1");  employee emp2 = new employee("jam","jon2");  employee emp3 = new employee("jam","jon3");  employee emp4 = new employee("jam","jon4");  employee emp5 = new employee("jam","jon5");  employee emp6 = new employee("pam","jin");  employee emp7 = new employee("pam","jin");  employee emp8 = new employee("pam","jin");  employee emp9 = new employee("pam","jin");  employee emp10 = new employee("pam","jin"); 

what best way find list of employee objects has "jam" first name , list of employee objects has "jin" last name.

    hashmap<string, list<employee>> firstnamecollected = new hashmap<>();     (employee e : yourarraylist) {         if (!firstnamecollected.containskey(e.firstname))             firstnamecollected.put(e.firstname, new arraylist<employee>());         firstnamecollected.get(e.firstname).add(e);     }     set<list<employee>> firstnameset = new hashset<>();     firstnameset.addall(firstnamecollected.values());