You can introduce a new method which actually does the job of moving from one to other and express the other two in terms of the common functionality.
pickup = move from in -> player
drop = move from player -> out
public void pickUp(Container in)
{
moveContainer(in, playerContainer);
}
public void dropContainer (Container out)
{
moveContainer(playerContainer, out);
}
public void moveContainer(Container from, Container to) {
if (to.returnSomething() == null) {
to.setSomething(from.returnSomething());
from.setSomething(null);
}
}