Difficult tasks using synchronized

In the Solution class, create a public static IntegerHolder class. IntegerHolder must accommodate an int (the variable name must be value), be thread safe, and be mutable. This class must have two public methods: get and set.

All of the Solution class's methods except the main method must be thread safe. Make it so both methods can be executed simultaneously by two different threads. "synchronized(this)" isn't suitable here. Use another object for the lock.

In the synchronized blocks, use the right lock.