android - Hashtable : How can use it with 2/3 different thread? -

on android have 1 hashtable , 2 thread can access that. - ui thread access containskey, , put - other thread access containskey, , put , iterator

i know hashtable thread safe, sure ?

one thing don't understand : why application doesn't blow if 1 thread doesn't see 1 value has been removed hashtable , thread iterates on object ?

how can define hashtable thread-safe if iterator isn't ?

edit : tell in more specific way problem, becasue in other way i'm not clear. following reported code of concurrenthashmap :

public concurrenthashmap<string,result> holder = new concurrenthashmap<string,result>();  class result {     public float goal = 0;     public float min = 0;     public float max = 0;     public float seconds = 0;     //lastaccess indicate time of last access of result     public float lastaccess = 0;     public boolean triggered = false; } 

now 1 thread b iterates every "x" seconds result object , each key stored in holder concurrethashmap .

other thread set new result new key or edit result existing one.

• i want operation of update result in atomic way, object inside hashmap scares me.

• ux thread remove item holder every x second. operation in way : created

  object mlock = new object();

in thread b

 syncrhonized(mlock)     {        //all thread b function.         // iterate on of holder item     } 

in other thread c when have call holder.clear() have done in way :

syncronized(mlock) {    holder.clear(); } 

• is correct way prevent thread b iterate on holder inconsistent data ?

it thread safe in high concurrent scenarios recommended use concurrenthashmap can see on official documentation