Java优学网Iterator遍历短文：从基础到实战，轻松掌握遍历技巧与避坑指南

List list = Arrays.asList("A", "B", "C"); Iterator iterator = list.iterator(); while(iterator.hasNext()) {

System.out.println(iterator.next());

}

List list = new ArrayList<>(Arrays.asList("A", "B", "C")); Iterator iterator = list.iterator();

while(iterator.hasNext()) {

String item = iterator.next();
if("B".equals(item)) {
    list.remove(item); // 这里会抛出ConcurrentModificationException
}

}

// 这两种写法在性能上没有本质区别 for (String item : list) {

System.out.println(item);

}

Iterator iterator = list.iterator(); while (iterator.hasNext()) {

String item = iterator.next();
System.out.println(item);

}

public class TreeNode {

String value;
List<TreeNode> children;

// 构造方法等省略

}

public class TreeIterator implements Iterator {

private Stack<TreeNode> stack = new Stack<>();

public TreeIterator(TreeNode root) {
    if (root != null) {
        stack.push(root);
    }
}

@Override
public boolean hasNext() {
    return !stack.isEmpty();
}

@Override
public TreeNode next() {
    if (!hasNext()) {
        throw new NoSuchElementException();
    }
    
    TreeNode current = stack.pop();
    // 将子节点逆序压栈，保证遍历顺序正确
    for (int i = current.children.size() - 1; i >= 0; i--) {
        stack.push(current.children.get(i));
    }
    
    return current;
}

}

public class ChunkedProductIterator implements Iterator {

private final ProductService productService;
private Iterator<Product> currentChunk;
private int currentPage = 0;
private final int chunkSize = 1000;

public ChunkedProductIterator(ProductService productService) {
    this.productService = productService;
    loadNextChunk();
}

private void loadNextChunk() {
    List<Product> chunk = productService.getProductsByPage(currentPage, chunkSize);
    currentChunk = chunk.iterator();
    currentPage++;
}

@Override
public boolean hasNext() {
    if (currentChunk.hasNext()) {
        return true;
    }
    // 尝试加载下一块
    loadNextChunk();
    return currentChunk.hasNext();
}

@Override
public Product next() {
    if (!hasNext()) {
        throw new NoSuchElementException();
    }
    return currentChunk.next();
}

}