add IterChain

CHANGELOG.md

@@ -10,6 +10,7 @@
 * 【all    】     JWT模块加入到all和bom包中(issue#1654@Github)
 * 【core   】     CollUtil删除所有Map相关操作
 * 【all    】     **重要！** 删除过期方法
+* 【core   】     增加IterChian类
 
 ### 🐞Bug修复
 

hutool-core/src/main/java/cn/hutool/core/collection/IterChain.java

@@ -0,0 +1,90 @@
+package cn.hutool.core.collection;
+
+import cn.hutool.core.lang.Chain;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.List;
+import java.util.NoSuchElementException;
+
+/**
+ * 组合{@link Iterator}，将多个{@link Iterator}组合在一起，便于集中遍历。<br>
+ * 来自Jodd
+ *
+ * @param <T> 元素类型
+ * @author looly, jodd
+ */
+public class IterChain<T> implements Iterator<T>, Chain<Iterator<T>, IterChain<T>> {
+
+	protected final List<Iterator<T>> allIterators = new ArrayList<>();
+
+	/**
+	 * 构造
+	 * 可以使用 {@link #addChain(Iterator)} 方法加入更多的集合。
+	 */
+	public IterChain() {
+	}
+
+	/**
+	 * Creates new composite iterator with provided iterators.
+	 */
+	@SafeVarargs
+	public IterChain(Iterator<T>... iterators) {
+		for (final Iterator<T> iterator : iterators) {
+			addChain(iterator);
+		}
+	}
+
+	@Override
+	public IterChain<T> addChain(Iterator<T> iterator) {
+		if (allIterators.contains(iterator)) {
+			throw new IllegalArgumentException("Duplicate iterator");
+		}
+		allIterators.add(iterator);
+		return this;
+	}
+
+	// ---------------------------------------------------------------- interface
+
+	protected int currentIter = -1;
+
+	@Override
+	public boolean hasNext() {
+		if (currentIter == -1) {
+			currentIter = 0;
+		}
+
+		final int size = allIterators.size();
+		for (int i = currentIter; i < size; i++) {
+			final Iterator<T> iterator = allIterators.get(i);
+			if (iterator.hasNext()) {
+				currentIter = i;
+				return true;
+			}
+		}
+		return false;
+	}
+
+	@Override
+	public T next() {
+		if (false == hasNext()) {
+			throw new NoSuchElementException();
+		}
+
+		return allIterators.get(currentIter).next();
+	}
+
+	@Override
+	public void remove() {
+		if (-1 == currentIter) {
+			throw new IllegalStateException("next() has not yet been called");
+		}
+
+		allIterators.get(currentIter).remove();
+	}
+
+	@Override
+	public Iterator<Iterator<T>> iterator() {
+		return this.allIterators.iterator();
+	}
+}