Iterable和iterator, enumerations-白红宇

Iterable和iterator, enumerations

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发布时间：2019-06-23

本文共 1999 字，大约阅读时间需要 6 分钟。

Iterable和iterator

Iterable定义了一个接口,表示该对象是可以用来遍历的,而实现该接口的类要返回一个iterator,来具体的实现遍历.

实现了Iterable接口的类可以和foreach配合使用.如果没有应用泛型的話,iterator返回的是object,需要类型转化.

应用

1.为我们自己的class创建多个iterator

public class GameCollection  { private Vector
    
      games; private Vector
     
       consoles;  private class Games implements Iterable
      
        {  @Override  public Iterator
       
         iterator() {   return games.iterator();  } }  private class Consoles implements Iterable
        
          {  @Override  public Iterator
         
           iterator() { return consoles.iterator(); } } public GameCollection() { games = new Vector
          
           (); consoles = new Vector
           
            (); } public void add(Game game) { games.add(game); } public void add(GameConsole console) { consoles.add(console); } public Games games() { return new Games(); } public Consoles consoles() { return new Consoles(); }}

GameCollection gc = new GameCollection();//Add games and consoles with gc.add()for (Game g : gc.games()) { System.out.println(g.getName());}for (GameConsole g : gc.consoles()) { System.out.println(g.getName());}

2.创建自己的iterator

public class CircularGamesIterator implements Iterator
    
      { private Vector
     
       list; private int currentPosition;  public CircularGamesIterator(Vector
      
        games) {  list = games;  currentPosition = 0; }  @Override public boolean hasNext() {  return currentPosition < list.size(); } @Override public Game next() {  Game el = list.elementAt(currentPosition);  currentPosition = (currentPosition + 1) % list.size();   return el; } @Override public void remove() { }}

public class GameCollection implements Iterable
    
      { private Vector
     
       games;  public GameCollection() {  games = new Vector
      
       (); }  public void add(Game game) {  games.add(game); } @Override public Iterator
       
         iterator() {  return new CircularGamesIterator(games); }}