!779 解决FilterIter 类中构造器filter 传入null 无法进行迭代器迭代

Merge pull request !779 from Joker7001/v5-dev

hutool-core/src/test/java/cn/hutool/core/collection/FilterIterTest.java

@@ -0,0 +1,31 @@
+package cn.hutool.core.collection;
+
+import org.junit.Test;
+
+import java.util.Iterator;
+
+/**
+ * {@link FilterIter} 单元测试
+ * @author chao.wang
+ */
+public class FilterIterTest {
+
+	@Test
+	public void checkFilterIter() {
+		Iterator<String> it = ListUtil.of("1", "2").iterator();
+		// filter 为null
+		FilterIter<String> filterIter = new FilterIter<>(it, null);
+		while (filterIter.hasNext()) {
+			System.out.println(filterIter.next());
+		}
+
+		System.out.println();
+		it = ListUtil.of("1", "2").iterator();
+		// filter 不为空
+		filterIter = new FilterIter<>(it, (key) -> key.equals("1"));
+		while (filterIter.hasNext()) {
+			System.out.println(filterIter.next());
+		}
+	}
+
+}