动态地向java中的arraylist添加更多值

Question

still a bit new with arrays and lists in java, I would like add elements to a list dynamically, so for example if I had code like this:

List<int[]> rowList = new ArrayList<int[]>();

rowList.add(new int[] { 1, 2, 3 });
rowList.add(new int[] { 4, 5, 6 });
rowList.add(new int[] { 7, 8 });

how would I dynamically add 1,2,3,4,5,6,7 etc? thanks in advance for the help

Answer 1

Simply use a List<Integer> to store the numbers directly:

 List<Integer> ints = new ArrayList<Integer>();
 ints.add(1);    // works with Java 1.5+, inboxing
 ints.add(2);

Or, if you want to keep your datastructure, wrap the numbers in short arrays:

 rowList.add(newValue(1));

where we have:

 private int[] newValue(int a) {
    int[] result = new int[1];
    result[0] = a;
    return result;
 }

Edit

Some more Java 1.5+ magic, using varargs and autoboxing:

 private int[] newValue(Integer... values) {
    int[] result = new int[values.length];
    for (int i = 0; i < result.length; i++)
       result[i] = values[i];
    return result
 }

Usage:

List<int[]> rowList = new ArrayList<int[]>();

rowList.add(newValues(10, 20, 30));
rowList.add(newValues(1,2,3,4,5,6,7));

Answer 2

If you want to add a new int[] to the list you will first have to create and fill it. If you don't know the length the array will be I would suggest an array that will dynamically add space as your reach its limit.

After you have created this array, just pass it as an argument. Should be straight forward.

Answer 3

You could use a for loop if you would like to add them without writing out every single number.

for(int i = 0; i < [however many you would like]; i++) {
    ints.add(i);
}

Answer 4

Something of this effect (using varargs if you have JDK 5 and higher).

public class ListUtils {
    public static void add(List<int[]> list, int... args) {
        if (list != null && args != null) {
            list.add(args);
        }
    }
}

Now, you can do

ListUtils.add(list, 1, 2, 3, 4, 5, 6, 7);

Answer 5

I am not sure of what you need but I hope this example will help you :

List<Integer> rowList = new ArrayList<Integer>();
Collections.addAll(rowList, ArrayUtils.toObject(new int[] { 1, 2, 3 }));
Collections.addAll(rowList, ArrayUtils.toObject(new int[] { 4, 5, 6 }));
Collections.addAll(rowList, ArrayUtils.toObject(new int[] { 7, 8 }));

ArraysUtils is a class of apache commons really usefull to deal with primitive and object arrays.

Regards, Diodfr