java - Is synchronization needed while reading if no contention could occur -


consider code sniper below:

package sync;  public class lockquestion {     private string mutable;      public synchronized void setmutable(string mutable) {         this.mutable = mutable;     }      public string getmutable() {         return mutable;     }    }

at time time1 thread thread1 update ‘mutable’ variable. synchronization needed in setter in order flush memory local cache main memory. @ time time2 ( time2 > time1, no thread contention) thread thread2 read value of mutable.

question – need put synchronized before getter? looks won’t cause issues - memory should date , thread2’s local cache memory should invalidated&updated thread1, i’m not sure.

rather wonder, why not use atomic references in java.util.concurrent?

(and it's worth, reading of happens-before not guarantee thread2 see changes mutable unless uses synchronized ... headache part of jls, use atomic references)


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