Java Collections

1. How to create generic array

• List<Integer>[] array = new List[len];
• import java.lang.reflect.Array;    ArrayList<Integer>[] array = (ArrayList<Integer>[])Array.newInstance(ArrayList.class, len);

 

2. Bit operations

• Get the odd number that is larger or equal to itself
  • x | 1
• Get the rightmost 1 of x
  • x & (-x)
• Remove the last bit from x 
  • x & (x-1)