add test

hutool-core/src/main/java/cn/hutool/core/collection/partition/Partition.java

@@ -42,6 +42,10 @@ public class Partition<T> extends AbstractList<List<T>> {
 	public int size() {
 		// 此处采用动态计算，以应对list变
 		final int size = this.size;
+		if(0 == size){
+			return 0;
+		}
+
 		final int total = list.size();
 		// 类似于判断余数，当总数非整份size时，多余的数>=1，则相当于被除数多一个size，做到+1目的
 		// 类似于：if(total % size > 0){length += 1;}

hutool-core/src/main/java/cn/hutool/core/collection/partition/package-info.java

@@ -0,0 +1,6 @@
+/**
+ * 列表分区或分段
+ *
+ * @author looly
+ */
+package cn.hutool.core.collection.partition;

hutool-core/src/test/java/cn/hutool/core/collection/partition/PartitionTest.java

@@ -0,0 +1,56 @@
+package cn.hutool.core.collection.partition;
+
+import cn.hutool.core.collection.ListUtil;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class PartitionTest {
+	@Test
+	public void sizeTest() {
+		final ArrayList<Integer> list = ListUtil.of(1, 2, 3, 4, 5);
+		final Partition<Integer> partition = new Partition<>(list, 4);
+		Assert.assertEquals(2, partition.size());
+	}
+
+	@Test
+	public void getSizeTest() {
+		List<Integer> mockedList = makingList(19);
+		Partition<Integer> partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(2, partition.size());
+
+		mockedList = makingList(11);
+		partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(2, partition.size());
+
+		mockedList = makingList(10);
+		partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(1, partition.size());
+
+		mockedList = makingList(9);
+		partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(1, partition.size());
+
+		mockedList = makingList(5);
+		partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(1, partition.size());
+	}
+
+	@Test
+	public void getZeroSizeTest() {
+		final List<Integer> mockedList = makingList(0);
+		final Partition<Integer> partition = new Partition<>(mockedList, 10);
+		Assert.assertEquals(0, partition.size());
+	}
+
+	private List<Integer> makingList(final int length) {
+		final List<Integer> list = ListUtil.of();
+		for (int i = 0; i < length; i++) {
+			list.add(i);
+		}
+
+		return list;
+	}
+}