jet.runtime.CollectionToArray Maven / Gradle / Ivy
package jet.runtime;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
public class CollectionToArray {
// Implementation copied from AbstractCollection
public static Object[] toArray(Collection collection) {
Object[] r = new Object[collection.size()];
Iterator it = collection.iterator();
for (int i = 0; i < r.length; i++) {
if (! it.hasNext()) // fewer elements than expected
return Arrays.copyOf(r, i);
r[i] = it.next();
}
return it.hasNext() ? finishToArray(r, it) : r;
}
public static T[] toArray(Collection collection, T[] a) {
// Estimate size of array; be prepared to see more or fewer elements
int size = collection.size();
T[] r = a.length >= size ? a :
(T[])java.lang.reflect.Array
.newInstance(a.getClass().getComponentType(), size);
Iterator it = collection.iterator();
for (int i = 0; i < r.length; i++) {
if (! it.hasNext()) { // fewer elements than expected
if (a != r)
return Arrays.copyOf(r, i);
r[i] = null; // null-terminate
return r;
}
r[i] = (T)it.next();
}
return it.hasNext() ? finishToArray(r, it) : r;
}
private static T[] finishToArray(T[] r, Iterator it) {
int i = r.length;
while (it.hasNext()) {
int cap = r.length;
if (i == cap) {
int newCap = ((cap / 2) + 1) * 3;
if (newCap <= cap) { // integer overflow
if (cap == Integer.MAX_VALUE)
throw new OutOfMemoryError
("Required array size too large");
newCap = Integer.MAX_VALUE;
}
r = Arrays.copyOf(r, newCap);
}
r[i++] = (T)it.next();
}
// trim if overallocated
return (i == r.length) ? r : Arrays.copyOf(r, i);
}
private CollectionToArray() {
}
}