Class AbstractIterator<E>

java.lang.Object
cloud.opencode.base.collections.AbstractIterator<E>
Type Parameters:
E - the type of elements returned by this iterator - 迭代器返回的元素类型
All Implemented Interfaces:
Iterator<E>
public abstract class AbstractIterator<E> extends Object implements Iterator<E>
AbstractIterator - Skeletal Iterator implementation requiring only computeNext() AbstractIterator - 只需实现 computeNext() 的骨架迭代器

Provides a simplified way to write an Iterator. Subclasses need only implement computeNext() and call endOfData() when iteration is complete.

提供了一种简化的方式来编写 Iterator。子类只需实现 computeNext()， 并在迭代结束时调用 endOfData()。

Features | 主要功能:

  • Lazy element computation - 延迟计算元素
  • Supports null elements - 支持 null 元素
  • peek() to inspect next element without consuming - peek() 查看下一个元素但不消费
  • Fail-safe state machine prevents misuse - 安全的状态机防止误用

Usage Examples | 使用示例:

// Iterate over an array range - 迭代数组范围
Iterator<String> iter = new AbstractIterator<>() {
    private int index = 0;
    private final String[] data = {"a", "b", "c"};

    @Override
    protected String computeNext() {
        return index < data.length ? data[index++] : endOfData();
    }
};

while (iter.hasNext()) {
    System.out.println(iter.next());
}

Performance | 性能特性:

  • Time complexity: O(1) per hasNext/next call - 时间复杂度: 每次 hasNext/next 调用 O(1)
  • Space complexity: O(1) overhead - 空间复杂度: O(1) 额外开销

Security | 安全性:

  • Thread-safe: No - 线程安全: 否
  • Null elements: Supported - 空元素: 支持
Since:
JDK 25, opencode-base-collections V1.0.3
Author:
Leon Soo www.LeonSoo.com
See Also:

  • Constructor Details

    • AbstractIterator

      public AbstractIterator()

  • Method Details

    • computeNext

      protected abstract E computeNext()
      Computes the next element in the iteration. 计算迭代中的下一个元素。

      Implementations must return the next element, or call endOfData() and return its result when there are no more elements.

      实现必须返回下一个元素，或者在没有更多元素时调用 endOfData() 并返回其结果。

      Returns:
      the next element, or the result of endOfData() 下一个元素，或 endOfData() 的结果

    • endOfData

      protected final E endOfData()
      Signals that the iteration is complete. 通知迭代已完成。

      Call this method from computeNext() when there are no more elements. Always return the result of this method from computeNext().

      当没有更多元素时，从 computeNext() 调用此方法。 始终从 computeNext() 返回此方法的结果。

      Returns:
      always null - 始终返回 null

    • hasNext

      public final boolean hasNext()

      Multiple calls to this method are idempotent; the underlying computeNext() is invoked at most once per element.

      对此方法的多次调用是幂等的；底层的 computeNext() 每个元素最多调用一次。

      Specified by:
      hasNext in interface Iterator<E>

    • next

      public final E next()
      Specified by:
      next in interface Iterator<E>
      Throws:
      NoSuchElementException - if iteration has no more elements 如果迭代没有更多元素

    • peek

      public final E peek()
      Returns the next element without advancing the iterator. 返回下一个元素但不推进迭代器。

      Subsequent calls to peek() return the same element until next() is called.

      在调用 next() 之前，对 peek() 的后续调用返回相同的元素。

      Returns:
      the next element - 下一个元素
      Throws:
      NoSuchElementException - if iteration has no more elements 如果迭代没有更多元素