Test.java

/* package whatever; // don't place package name! */

import java.util.*;
import java.lang.*;
import java.io.*;

/* Name of the class has to be "Main" only if the class is public. */
class Test
{
	public static void main (String[] args) throws java.lang.Exception
	{
		LinkedList<LinkedList<String>> squares = new LinkedList<>();
// LinkedList<LinkedList<String>> squares = new LinkedList<LinkedList<String>>();

		squares.add(new LinkedList<>());
		squares.get(0).add("hoge");

		System.out.println(squares.get(0).get(0)); // hoge
	}
}