Iterator object and Iterator generator object

Iterator object and Iterator generator object

Directory:

Use of Iterator

   
"Iteration string set
    
Iteration object set
 

Graph and Principle Analysis of the iterator

Java iterator source code

Iterator usage:

   
"Iteration string set
 

        
Import java. util. arrayList; import java. util. collection; import java. util. iterator;/*** set iteration ** the Iterator iterator () set's dedicated Iterator ** E next () gets the current element of the pointer, the pointer moves to the next element * NoSuchElementException without such an element, because you have found the last * boolean hasNext (). If there are still elements that can be iterated, true is returned. */Public class IteratorDemo {public static void main (String [] args) {// create a Collection c = new ArrayList (); // Add the element c to the Collection. add ("hello"); c. add ("world"); c. add ("java"); // Iterator iterator () Iterator, set the dedicated iteration method Iterator it = c. iterator (); // Iterator is an interface, and the iterator () method returns an implementation class. Here it is a multi-state System. out. println (it. next (); System. out. println (it. next (); System. out. println (it. next (); // System. out. println (it. next (); // String s = null; // while (it. hasNext () {// s = (String) it. next (); // System. out. println (s );//}}}
  

  
Iteration object set

      
Import java. util. arrayList; import java. util. collection; import java. util. iterator;/***** exercise: Use a set to store five student objects, traverse students, and use an Iterator to traverse students. ** Question 1: Can a while loop be used? * Question 2: Do not use the it. next () method twice, because each use accesses an object. */Public class IteratorTest {public static void main (String [] args) {// create Collection object Collection c = new ArrayList (); // create Student s1 = new Student ("Lin Qing", 26); Student s2 = new Student ("Zhou runfa", 45 ); student s3 = new Student ("Huang jianxiang", 25); Student s4 = new Student ("Xie Yunfeng", 30); Student s5 = new Student ("Faye Wong", 30 ); // Add the student object to the set. add (s1); c. add (s2); c. add (s3); c. add (s4); c. add (s5); // get the set Iterator it = c. iterator (); // use the iterator to traverse the Student set Student s = null; while (it. hasNext () {s = (Student) it. next (); System. out. println (s. getName () + "------" + s. getAge (); // NoSuchElementException do not use it multiple times. next () method // System. out. println (Student) it. next ()). getName () + "-----" + (Student) it. next ()). getAge ();} // for Loop rewriting/* Student s = null; for (Iterator it = c. iterator (); it. hasNext ();) {s = (Student) it. next (); System. out. println (s. getName () + "------" + s. getAge ());}*/}}
    
 

  
//bean

      
public class Student {    private String name;    private int age;            public Student() {        super();    }    public Student(String name, int age) {        super();        this.name = name;        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    }
  

 

Graph and Principle Analysis of the iterator

Java iterator source code

      
Public interface Inteator {boolean hasNext (); Object next ();} public interface Iterable {Iterator iterator ();} public interface Collection extends Iterable {Iterator iterator ();} public interface List extends Collection {Iterator iterator ();} public class ArrayList implements List {// The implementation class contains the Iterator interface implementation public Iterator iterator () {return new Itr ();} private class Itr implements Iterator {// is an internal class and is a private public boolean hasNext () not known to outsiders () {} public Object next () {}} Collection c = new ArrayList (); c. add ("hello"); c. add ("world"); c. add ("java"); Iterator it = c. iterator (); // new Itr (); while (it. hasNext () {String s = (String) it. next (); System. out. println (s );}