Java Record -58-iterator iterator

Iterator iterators

An iterator is a design pattern that is an object that can traverse and select objects in a sequence, and the developer does not need to know the underlying structure of the sequence. Iterators are often referred to as "lightweight" objects because they are less expensive to create.

public interface iterator<e>

An iterator that iterates over the collection. Iterators replace the enumeration in the Java collections Framework. Iterators are two points different from enumerations:

• Iterators allow callers to take advantage of well-defined semantics to remove elements from the collection that iterators point to during iterations.

• The method name has been improved.

The methods that are included:

Boolean Hasnext () returns True if there are still elements that can iterate.

E Next () returns the next element of the iteration.

void Remove () removes the last element returned by the iterator from the collection that the iterator points to (optional action).

Use the iteration function:

Before you access a class set through an iterative function, you must get an iterative function. Each collection class provides a iterator () function that returns an iterative function on the class set header. With this iterative function object, you can access each element in the class set, one element at a time. You typically use an iterative function to loop through the contents of a class set, in the following steps:

1. The iterative function of the class set header is obtained by invoking the iterator () method of the class set;

2. Create a loop that calls the Hasnext () method, and iterate as long as Hasnext () returns True.

Inside the loop, each element is obtained by invoking the next () method.

Iterators are typically applied to a while loop:

Iterator iter = Hashset.iterator ();            while (Iter.hasnext ()) {Object obj = Iter.next ();        System.out.println (obj); }

Java Record -58-iterator iterator