Java Collection Collection Detailed 3

 Packagecn.itcast_03; Public  class Student {    //Member variables    PrivateString name;Private intAge//Construction method     Public Student() {Super(); } Public Student(String name,intAge) {Super(); This. name = name; This. Age = Age; }//Member Method    //GetXxx ()/setxxx ()     PublicStringGetName() {returnName } Public void SetName(String name) { This. name = name; } Public int Getage() {returnAge } Public void Setage(intAge) { This. Age = Age; }@Override     PublicStringtoString() {return "Student [name="+ name +", age="+ Age +"]"; }}

 Packagecn.itcast_03;ImportJava.util.ArrayList;ImportJava.util.Collection;ImportJava.util.Iterator;/* * Exercise: Store 5 student objects in a collection and traverse the student objects. Iterate with iterators. * * Note: * A: Your class name should not be the same as the class name in the API we are learning to use. * B: When copying the code, it is easy to import the package that the class is in, which is prone to problems that cannot be understood. */ Public  class iteratortest {     Public Static void Main(string[] args) {//Create collection ObjectCollection C =NewArrayList ();//Create student ObjectsStudent S1 =NewStudent ("Brigitte", -); Student s2 =NewStudent ("The Wind", -); Student s3 =NewStudent ("Make the fox Rush", -); Student S4 =NewStudent ("Wu Xin", -); Student S5 =NewStudent ("Lynn Song", A);//Add students to the collectionC.add (S1);        C.add (S2);        C.add (S3);        C.add (S4); C.add (S5);//TraversalIterator it = C.iterator (); while(It.hasnext ()) {//System.out.println (It.next ());Student s = (Student) it.next (); System.out.println (S.getname () +"---"+ s.getage ()); }    }}

Package CN. Itcast_03;Import Java. Util. ArrayList;Import Java. Util. Collection;Import Java. Util. Iterator;/* * Question 1: Can I use the while loop to write this program, can I have a for loop? * Issue 2: Do not use the It.next () method multiple times because each use is to access an object. */public class IteratorTest2 {public static void main (string[] args) {//Create collection Object Collection c = new Arrayl IST ();Create student object Student S1 = new Student ("Brigitte", -);Student s2 = new Student ("The Wind", -);Student s3 = new Student ("Make the fox Rush", -);Student S4 = new Student ("Wu Xin", -);Student S5 = new Student ("Lynn Song", A);Add students to the collection C. Add(S1);C. Add(S2);C. Add(S3);C. Add(S4);C. Add(S5);Traverse Iterator it = C. Iterator();while (it. Hasnext()) {Student s = (Student) it. Next();System. out. println(s. GetName() +"---"T. Getage());Nosuchelementexception don't use it multiple times. Next() method//System. out. println((Student) it. Next()). GetName() +"---"+ ((Student) it. Next()). Getage());}//System. out. println("----------------------------------");For loop overwrite//for (Iterator it = C. Iterator(); It.hasnext ();) {Student s = (Student) it. Next();System. out. println(s. GetName() +"---"+ S. Getage());// }    }}

Package CN. Itcast_03;Import Java. Util. ArrayList;Import Java. Util. Collection;Import Java. Util. Iterator;/* * Iterator Iterator (): iterator, the private traversal method of the collection * Object next (): Gets the element and moves to the next position. * Nosuchelementexception: No such element, because you have found the last. * Boolean hasnext (): Returns True if there are still elements that can iterate. (*/public class Iteratordemo {public static void main (string[] args) {//Create collection Object Collection c = new Arrayli St ();Create and add element//String s ="Hello";C. Add(s);C. Add("Hello");C. Add("World");C. Add("Java");Iterator Iterator (): iterator, private traversal of the collection Iterator it = C. Iterator();//The actual return is definitely a subclass object, here is the polymorphicObject obj = it. Next();System. out. println(obj);System. out. println(It. Next());System. out. println(It. Next());System. out. println(It. Next());System. out. println(It. Next());The last one should not be written, so, we should be in every acquisition before, if there is a judgment on it//to determine whether there is the next element, there is to get, not to ignore it//if (it. Hasnext()) {//System. out. println(It. Next());}//if (it. Hasnext()) {//System. out. println(It. Next());}//if (it. Hasnext()) {//System. out. println(It. Next());}//if (it. Hasnext()) {//System. out. println(It. Next());}//if (it. Hasnext()) {//System. out. println(It. Next());}//The final version of code while (it. Hasnext()) {//System. out. println(It. Next());string s = (string) it. Next();System. out. println(s);}    }}

The source of the iterator is as follows:

 Public  interface inteator {    BooleanHasnext (); 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 {     PublicIteratoriterator() {return NewItr (); }Private  class Itr implements Iterator {         Public Boolean Hasnext() {} PublicObjectNext() {}}}collection c =NewArrayList (); 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);}

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

Java Collection Collection Detailed 3