java - HashMap method/ parameter -

see following class definition using hashmap.

why not necessary pass formal parameters of methods local parameters did in second method?

import java.util.hashmap;  public class maptester {     private hashmap<string, string> phonebook = new hashmap<string, string> ();      public maptester()     {         phonebook.put("homer jay simpson", "(531) 9392 4587");         phonebook.put("charles montgomery burns", "(531) 5432 1945");         phonebook.put("apu nahasapeemapetilon", "(531) 4234 4418");             }          public void enternumber(string name, string number)     {                phonebook.put(name, number);     }      public string lookupnumber(string _name)      {                 name = _name;         return phonebook.get(name);     }    } 

it not necessary copy parameter local variable, because have 2 copies of same variable (name , _name) while need one.

moreover, need change line to

string name = _name; 

to make compile.