Initialize ArrayList in Java
package xiaoling;
import ;
import ;
import ;
public class ListTest{
public static void main(String[] args){
List<List<Integer>> list = new ArrayList<>();
for (int num=0; num<10; ++num){
(new ArrayList((num, num+1)));
}
(list);
}
}
The results of the run are: [[0, 1], [1, 2], [2, 3], [3, 4], [4, 5], [5, 6], [6, 7], [7, 8], [8, 9], [9, 10]]
Extended Learning:
Java Quickly create List collections
The code of a certain case in the program is as follows:
Map<String, List<CronTrigger>> tMap = new HashMap<String, List<CronTrigger>>();
(name, (new CronTrigger[] { trigger }));
The program run throws an exception:
Cause of error:
Methods are used to quickly create Lists, but the ArrayList returned by this method is not an object, but an inner class of Arrays.
We can check the source code
:
@SafeVarargs
public static <T> List<T> asList(T... a) {
return new ArrayList<>(a);
}
---------------------------------------------------
private static class ArrayList<E> extends AbstractList<E>
implements RandomAccess,
{
private static final long serialVersionUID = -2764017481108945198L;
private final E[] a;
ArrayList(E[] array) {
if (array==null)
throw new NullPointerException();
a = array;
}
.....
In the above code, you can see that the inner class ArrayList inherits AbstractList
Thank you for your study and support.