java - 关于 "for"语句中迭代器对象的问题

Question

我试图理解一个java程序，它有一个代码段，例如

for (final Document document : cluster.getDocuments())  {  
    if (documentsShown >= maxNumberOfDocumentsToShow)  {  
        break;  
    }  
    displayDocument(level + 1, document);  
    documentsShown++;  
}  

这是否意味着 cluster.getDocuments() 必须是迭代器对象？

Answer 1

它必须是一个可迭代对象(即集合或数组)。基本上，

It's commonly used to iterate over an array or a Collections class (eg, ArrayList). It can also iterate over anything that implements the Iterable interface (must define iterator() method). Many of the Collections classes (eg, ArrayList) implement Iterable, which makes the for-each loop very useful. You can also implement Iterable for your own data structures.

Reference

All Known Implementing Classes of Iterable