如何把2行字母读进一个2维的ArrayList

文件里面有很多行字.如果只想读前2行,把第一行字母(char)读进arraylist,再把第二行的char读进另一个arraylist应该怎么做
我想过用sanner,bufferedreader和FileImageInputStream,应该用那个,那一个method可以识别一行已经读完?

import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class Test {
public static void main(String[] args) {
List<Character> list1 = new ArrayList<Character>();
List<Character> list2 = new ArrayList<Character>();
BufferedReader br;
try {
br = new BufferedReader(new InputStreamReader(new FileInputStream("in.txt")));
String line;

if (null != (line = br.readLine())) {
char[] tmp = line.toCharArray();
for (int i = 0; i < tmp.length; i++) {
list1.add(tmp[i]);
}
}

if (null != (line = br.readLine())) {
char[] tmp = line.toCharArray();
for (int i = 0; i < tmp.length; i++) {