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package com.vaadin.data;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import com.vaadin.data.Container.Indexed;
/**
* Contains helper methods for containers that can be used to ease development
* of containers in Vaadin.
*
* @since 7.0
*/
public class ContainerHelpers {
/**
* Get a range of item ids from the container using
* {@link Indexed#getIdByIndex(int)}. This is just a helper method to aid
* developers to quickly add the required functionality to a Container
* during development. This should not be used in a "finished product"
* unless fetching an id for an index is very inexpensive because a separate
* request will be performed for each index in the range.
*
* @param startIndex
* index of the first item id to get
* @param numberOfIds
* the number of consecutive items whose ids should be returned
* @param container
* the container from which the items should be fetched
* @return A list of item ids in the range specified
*/
public static List<?> getItemIdsUsingGetIdByIndex(int startIndex,
int numberOfIds, Container.Indexed container) {
if (container == null) {
throw new IllegalArgumentException(
"The given container cannot be null!");
}
if (startIndex < 0) {
throw new IndexOutOfBoundsException(
"Start index cannot be negative! startIndex=" + startIndex);
}
if (startIndex > container.size()) {
throw new IndexOutOfBoundsException(
"Start index exceeds container size! startIndex="
+ startIndex + " containerLastItemIndex="
+ (container.size() - 1));
}
if (numberOfIds < 1) {
if (numberOfIds == 0) {
return Collections.emptyList();
}
throw new IllegalArgumentException(
"Cannot get negative amount of items! numberOfItems="
+ numberOfIds);
}
// not included in the range
int endIndex = startIndex + numberOfIds;
if (endIndex > container.size()) {
endIndex = container.size();
}
ArrayList<Object> rangeOfIds = new ArrayList<Object>();
for (int i = startIndex; i < endIndex; i++) {
Object idByIndex = container.getIdByIndex(i);
if (idByIndex == null) {
throw new RuntimeException(
"Unable to get item id for index: "
+ i
+ " from container using Container.Indexed#getIdByIndex() "
+ "even though container.size() > endIndex. "
+ "Returned item id was null. "
+ "Check your container implementation!");
}
rangeOfIds.add(idByIndex);
}
return Collections.unmodifiableList(rangeOfIds);
}
}
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