package at.irian.misc.javabug; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; public class Main { public static void main(String[] args) { Map map = new ConcurrentHashMap<>(16); map.computeIfAbsent( "AaAa", key -> { return map.computeIfAbsent( "BBBB", key2 -> 42); } ); } }