Java container and iterator interface detailed analysis using

Iterator interface:

So the container class that implements the collection interface has a iterator method to return an object that implements the iterator interface.

The iterator object is called an iterator to facilitate the traversal of elements within a container.

The iterator interface defines the following methods:

  
   
   

   
    
   
    
    

      Boolean hasnext (); To determine if there are elements on the right side of the cursor 
     
Object Next (); Returns the element to the right of the cursor and moves the cursor to the next position 
     
void Remove (); Deletes the element to the left of the cursor, which can only be executed once after the next action is executed 
    
  
   
   

Practice:

   
    
    

    
     Import java.util.*;
    
     
     
public class testiterator{
    
     
     
    public static void Main (string[] args) {
    
     
     
        Collection C = new HashSet ();
    
     
     
        C.add ("Hello");
    
     
     
        C.add ("World");
    
     
     
        C.add ("!");
    
     
     
        Iterator i = C.iterator ();
    
     
     
        while (I.hasnext ()) {
    
     
     
            string n = (string) i.next ();
    
     
     
            System.out.println (n);
    
     
     
        }
    
     
     
    }
    
     
     
}
   
    
    

Device: an instance of a series of classes provided by the Java API that is used to store objects in a program. The container class provided by the JDK is in the Java.util package. The collection interface defines methods for accessing a set of objects, and its Sub-interface set and list define the storage mode respectively.

The data objects in the set are not ordered and cannot be duplicated.

The data objects in the list are in order and can be duplicated.

The map interface defines a method for storing "key (value) mapping pairs"
Collection The method defined in the interface:

   
    
    

    
         int size ();  How many elements
    
     
     
    Boolean IsEmpty ();//IS NULL
    
     
     
    void Clear ();
    
     
     
    Boolean contains (object element);//Whether or not to contain an object
    
     
     
    Boolean Add (object element);//Add Element
    
     
     
    Boolean remove (object element);//delete
    
     
     
    Iterator iterator ();
    
     
     
    Boolean Containsall (collection C);//is not containing the elements in another collection
    
     
     
    Boolean AddAll (collection C);//Add All
    
     
     
    Boolean RemoveAll (collection C);//Delete all
    
     
     
    Boolean Retainall (collection C);//Find Intersection
    
     
     
    Object[] ToArray ();//Convert to object class array
   
    
    

The collection is loaded with objects and cannot be the underlying data type. Because the underlying data type is stored on the stack, it can be retracted at any time.

The Remove () method calls the Equals () method, so the class that you implement overrides the Equals method and the Hashcode () method.