[scanner类](%E9%9D%A2%E5%90%91%E5%AF%B9%E8%B1%A1/scanner%E7%B1%BB.md) [Random类](java%E5%9F%BA%E7%A1%80%E7%B1%BB/Random%E7%B1%BB.md) [System类](system%E7%B1%BB.md) [Runtime类](java%E5%9F%BA%E7%A1%80%E7%B1%BB/Runtime%E7%B1%BB.md) [Comparable接口](java%E5%9F%BA%E7%A1%80%E7%B1%BB/Comparable%E6%8E%A5%E5%8F%A3.md) [Comparator接口](java%E5%9F%BA%E7%A1%80%E7%B1%BB/Comparator%E6%8E%A5%E5%8F%A3.md) [MessageFormat类](java%E5%9F%BA%E7%A1%80%E7%B1%BB/MessageFormat%E7%B1%BB.md) [NumberFormat](../NumberFormat.md)