Code to flatten a list in Java, with and without recursion

Sat, 17 Apr 2010 23:42:16 +0000

Recently had someone ask me to solve this problem: assume you have a list of objects, some of which may be lists of arbitrary depths. Write a function to return the list “flattened,” so sublists are all in the “main” list. I solved it recursively pretty easily, but it took some thought to do it without recursion. My solutions are below.

package com.evanhoffman.listflattener;

import java.util.LinkedList; import java.util.List; import java.util.ListIterator;

import org.apache.log4j.BasicConfigurator; import org.apache.log4j.Logger;

Recursive on Evan Hoffman

Code to flatten a list in Java, with and without recursion