add class

hutool-core/src/test/java/cn/hutool/core/convert/CastUtilTest.java

@@ -0,0 +1,45 @@
+package cn.hutool.core.convert;
+
+import cn.hutool.core.collection.ListUtil;
+import cn.hutool.core.collection.SetUtil;
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.io.Serializable;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+
+public class CastUtilTest {
+	@Test
+	public void testCastToSuper() {
+		Collection<Integer> collection= ListUtil.of(1,2,3);
+		List<Integer> list = ListUtil.of(1, 2, 3);
+		Set<Integer> set = SetUtil.of(1, 2, 3);
+		Map<Integer, Integer> map = new HashMap<>();
+		map.put(1, 1);
+
+		Collection<Number> collection2 = CastUtil.castUp(collection);
+		Assert.assertSame(collection, collection2);
+
+		Collection<Integer> collection3 = CastUtil.castDown(collection2);
+		Assert.assertSame(collection2, collection3);
+
+		List<Number> list2 = CastUtil.castUp(list);
+		Assert.assertSame(list, list2);
+		List<Integer> list3 = CastUtil.castDown(list2);
+		Assert.assertSame(list2, list3);
+
+		Set<Number> set2 = CastUtil.castUp(set);
+		Assert.assertSame(set, set2);
+		Set<Integer> set3 = CastUtil.castDown(set2);
+		Assert.assertSame(set2, set3);
+
+		Map<Number, Serializable> map2 = CastUtil.castUp(map);
+		Assert.assertSame(map, map2);
+		Map<Integer, Number> map3 = CastUtil.castDown(map2);
+		Assert.assertSame(map2, map3);
+	}
+}