Add elements in multidimensional ArrayList in Java

Question

I want to store some values (actually a message) using list in Java. I want to store something like:

{user1, message, user2, time}
{user1, message, user4, time}
{user3, message, user1, time} 

I have declared an arraylist like this:

public List<List<String>> message = new ArrayList<List<String>>();

How can I add values in this list and how can I get a specific row (let's say the second row) of this list?

I've tried:

    message.get(0).add(msg, target,time);

but I get an error:

"The method add(String) in the type List is not applicable for the arguments (String, String, Integer)"

Answer 1

You could do something like:

List<Object[]> list = new ArrayList<Object[]>();        
Object[] ob = new Object[4];
ob[0] = "user1";
ob[1] = "messge1";
ob[2] = "user2";
ob[3] = "time1";

list.add(ob);       

ob = new Object[4];
ob[0] = "user2";
ob[1] = "messge2";
ob[2] = "user4";
ob[3] = "time2";
list.add(ob);

// Output the values
for(Object[] o : list){
    System.out.print(o[0] + "\t");
    System.out.print(o[1] + "\t");
    System.out.print(o[2] + "\t");
    System.out.print(o[3] + "\n");
}

and the output will be:

user1 messge1 user2 time1

user2 messge2 user4 time2

Answer 2

by

message.get(0);

you are retriving the first list in list of list referred by message

List has add(T object) method so you can't pass all 3 Objects in one call, one way to do is

message.get(0).add(msg);
message.get(0).add(target);
message.get(0).add(time);