如何将一个数组列表(size=1000)拆分为多个相同大小(=10)的数组列表?
ArrayList<Integer> results;
如何将一个数组列表(size=1000)拆分为多个相同大小(=10)的数组列表?
ArrayList<Integer> results;
当前回答
这对我很有用
/**
* Returns List of the List argument passed to this function with size = chunkSize
*
* @param largeList input list to be portioned
* @param chunkSize maximum size of each partition
* @param <T> Generic type of the List
* @return A list of Lists which is portioned from the original list
*/
public static <T> List<List<T>> chunkList(List<T> list, int chunkSize) {
if (chunkSize <= 0) {
throw new IllegalArgumentException("Invalid chunk size: " + chunkSize);
}
List<List<T>> chunkList = new ArrayList<>(list.size() / chunkSize);
for (int i = 0; i < list.size(); i += chunkSize) {
chunkList.add(list.subList(i, i + chunkSize >= list.size() ? list.size()-1 : i + chunkSize));
}
return chunkList;
}
例如:
List<Integer> stringList = new ArrayList<>();
stringList.add(0);
stringList.add(1);
stringList.add(2);
stringList.add(3);
stringList.add(4);
stringList.add(5);
stringList.add(6);
stringList.add(7);
stringList.add(8);
stringList.add(9);
List<List<Integer>> chunkList = getChunkList1(stringList, 2);
其他回答
private ArrayList<List<String>> chunkArrayList(ArrayList<String> arrayToChunk, int chunkSize) {
ArrayList<List<String>> chunkList = new ArrayList<>();
int guide = arrayToChunk.size();
int index = 0;
int tale = chunkSize;
while (tale < arrayToChunk.size()){
chunkList.add(arrayToChunk.subList(index, tale));
guide = guide - chunkSize;
index = index + chunkSize;
tale = tale + chunkSize;
}
if (guide >0) {
chunkList.add(arrayToChunk.subList(index, index + guide));
}
Log.i("Chunked Array: " , chunkList.toString());
return chunkList;
}
例子
ArrayList<String> test = new ArrayList<>();
for (int i=1; i<=1000; i++){
test.add(String.valueOf(i));
}
chunkArrayList(test,10);
输出
分块:[[1,2,3,4,5,6,7,8,9,10),(11、12、13、14、15、16、17、18、19、20],[21日,22日,23日,24日,25日,26日,27日,28日,29日,30日],[第三十一条、第三十二条、第三十三,34岁,35岁,36岁,37岁,38岁,39岁,40],[41、42、43、44、45、46岁,47岁,48岁,49岁,50],[51岁,52岁,53岁,54岁,55岁,56岁,57岁的58岁的59岁60],[61,62,63,64,65,66,67,68,69,70],[71,72,73,74,75,76,77,78,79,80],[81,82,83,84,85,86,87,88,89,90],[91,92,93,94,95,96,97,98,99,100 ], .........
你会在日志里看到的
import org.apache.commons.collections4.ListUtils;
ArrayList<Integer> mainList = .............;
List<List<Integer>> multipleLists = ListUtils.partition(mainList,100);
int i=1;
for (List<Integer> indexedList : multipleLists){
System.out.println("Values in List "+i);
for (Integer value : indexedList)
System.out.println(value);
i++;
}
List<List<Integer>> allChunkLists = new ArrayList<List<Integer>>();
List<Integer> chunkList = null;
int fromIndex = 0;
int toIndex = CHUNK_SIZE;
while (fromIndex < origList.size()) {
chunkList = origList.subList(fromIndex, (toIndex > origList.size() ? origList.size() : toIndex));
allChunkLists.add(chunkList);
fromIndex = toIndex;
toIndex += CHUNK_SIZE;
}
没有库,只有Java的subList()。toIndex需要适当地有界,以避免在subList()中出现越界错误。
**Divide a list to lists of n size**
import java.util.AbstractList;
import java.util.ArrayList;
import java.util.List;
public final class PartitionUtil<T> extends AbstractList<List<T>> {
private final List<T> list;
private final int chunkSize;
private PartitionUtil(List<T> list, int chunkSize) {
this.list = new ArrayList<>(list);
this.chunkSize = chunkSize;
}
public static <T> PartitionUtil<T> ofSize(List<T> list, int chunkSize) {
return new PartitionUtil<>(list, chunkSize);
}
@Override
public List<T> get(int index) {
int start = index * chunkSize;
int end = Math.min(start + chunkSize, list.size());
if (start > end) {
throw new IndexOutOfBoundsException("Index " + index + " is out of the list range <0," + (size() - 1) + ">");
}
return new ArrayList<>(list.subList(start, end));
}
@Override
public int size() {
return (int) Math.ceil((double) list.size() / (double) chunkSize);
}
}
Function call :
List<List<String>> containerNumChunks = PartitionUtil.ofSize(list, 999)
详情:https://e.printstacktrace.blog/divide-a-list-to-lists-of-n-size-in-Java-8/
我猜你遇到的问题是命名100个数组列表并填充它们。您可以创建一个数组列表数组,并使用循环填充每个数组列表。
最简单(也是最愚蠢的)的方法是这样的:
ArrayList results = new ArrayList(1000);
// populate results here
for (int i = 0; i < 1000; i++) {
results.add(i);
}
ArrayList[] resultGroups = new ArrayList[100];
// initialize all your small ArrayList groups
for (int i = 0; i < 100; i++) {
resultGroups[i] = new ArrayList();
}
// put your results into those arrays
for (int i = 0; i < 1000; i++) {
resultGroups[i/10].add(results.get(i));
}