Connect multiple arraylist to one single array list

Here is a complete, executable, demo for you. You should be able to compile and run as is. I didn't add comments or error checking, but it should do what you ask. Whether a lists of lists is the best thing for your current situation I don't know. The fact that your rows have both names AND ages makes me think that you don't want a list of lists, but rather a list of row objects of a particular class. (Alternatively you can use List<?> or List<Object> everywhere....)

Nevertheless, the following may be of interest to you. You might be able to use it, or it might scare you away from a list of lists approach. :)

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * A ragged 2-D table of strings that supports "views" (arbitrary rows).
 *
 * WARNING: no error checking.  This is just a sketch.
 */
public class Table {

    private List<List<String>> data;
    private List<Integer> activeRows = new ArrayList<Integer>();

    public Table(List<List<String>> data) {
        this.data = data;
    }

    public void setActiveRows(List<Integer> activeRows) {
        this.activeRows = activeRows;
    }

    public void update(int row, int column, String value) {
        data.get(row).set(column, value);
    }

    public void show() {
        for (Integer row: activeRows) {
            System.out.println(data.get(row));
        }
    }

    /**
     * DEMO.  Normally we don't put main methods inside a class.  This is just a sketch.
     */
    public static void main(String[] args) {
        List<List<String>> a = Arrays.asList(
            Arrays.asList("abc", "def", "ghi"),
            Arrays.asList("ABC", "DEF", "GHI"),
            Arrays.asList("zzz", "yyy", "xxx"),
            Arrays.asList("dog", "cat", "rat")
        );

        // Make two tables that share the same data
        Table t1 = new Table(a);
        Table t2 = new Table(a);

        // t1 will have all four rows; t2 just two of them.
        t1.setActiveRows(Arrays.asList(0, 1, 2, 3));
        t2.setActiveRows(Arrays.asList(1, 3));

        // Show them
        t1.show();
        System.out.println();
        t2.show();
        System.out.println();

        // Now change part of t1 and show that this is reflected in t2.
        t1.update(1, 2, "NEWVALUE");

        // And show them again
        t1.show();
        System.out.println();
        t2.show();
        System.out.println();
    }
}

Output is:

[abc, def, ghi]
[ABC, DEF, GHI]
[zzz, yyy, xxx]
[dog, cat, rat]

[ABC, DEF, GHI]
[dog, cat, rat]

[abc, def, ghi]
[ABC, DEF, NEWVALUE]
[zzz, yyy, xxx]
[dog, cat, rat]

[ABC, DEF, NEWVALUE]
[dog, cat, rat]