import java.util.List; // This is the interface that allows for creating nested lists. // You should not implement it, or speculate about its implementation public interface NestedInteger { // @return true if this NestedInteger holds a single integer, rather than a nested list. public boolean isInteger(); // @return the single integer that this NestedInteger holds, if it holds a single integer // Return null if this NestedInteger holds a nested list public Integer getInteger(); // @return the nested list that this NestedInteger holds, if it holds a nested list // Return null if this NestedInteger holds a single integer public List getList(); }