Xin questions

• Necessity of <? super T> type in Collections.copy [duplicate]
• Errors occur when calling print(List<T> a, T b) with different T class
• Differences between `copy(List<? super T> dest, List<? extends T> src) ` and `copy(List<T> dest, List<? extends T> src)`
• What is HALF_EVEN rounding for? [closed]
• Do not understand the source code of Arrays.copyOf

Xin answers