https://sven31316.github.io/2017/01/21/%E3%80%90Java-You-Don-t-Know-Item-1%E3%80%91%E4%B8%BA%E4%BB%80%E4%B9%88long%E7%B1%BB%E5%9E%8B%E7%9A%84%E5%8F%98%E9%87%8F%E5%9C%A8%E8%B5%8B%E5%80%BC%E6%97%B6%E6%95%B0%E5%80%BC%E5%B8%B8%E9%87%8F%E8%A6%81%E5%8A%A0%E2%80%9CL%E2%80%9D/