参考 https://srvaroa.github.io/jvm/java/openjdk/biased-locking/2017/01/30/hashCode.html https://www.cnblogs.com
wiki.openjdk.java.net/display/HotSpot/Synchronization [5]默认hashCode生成方式: https://srvaroa.github.io/jvm/java/openjdk/biased-locking