1.定義#

提供一種方法訪問一個容器對象中各個元素，而又不需要暴露該對象的內(nèi)部細節(jié)。大部分語言中已經(jīng)在常用數(shù)據(jù)結(jié)構(gòu)類型中實現(xiàn)，不需要自己動手實現(xiàn)。主要用于遍歷一個容器對象。實現(xiàn)中迭代器類主要用一個游標(biāo)在容器元素間前后移動。

2.類圖#

類圖

3.實現(xiàn)#

3.1抽象迭代器##

public interface Iterator{
  public Object next();
  public boolean hasNext();
  public boolean remove();
}

3.2具體迭代器##

public class ConcreteIterator implements Iterator {
  private ArrayList<T> arrayList = new ArrayList<T>();
  
  public int cursor = 0;
  public ConcreteIterator(ArryaList<T> _arrayList){
    this.arrayList = _arrayList;
  }

  public boolean hasNext(){
    if(this.cursor == this.arrayList.size())
    {
      return false;
    }else{
      return true;
    }
  }

  public Object next(){
    Object result = null;
    if(this.hasNext){
      result = this.arrayList.get(this.cursor++);
    }else{
      result = null;
    }
    return result;
  }

  public boolean remove(){
    this.arryaList.remove(this.cursor--);
  }
}

3.3抽象容器類##

public interface Aggregate{
  public void add(Object object);
  public void remove(Object object);
  public Iterator iterator();
}

3.4具體容器類##

public class ConcreteAggregate implements Aggregate{
  private ArrayList arrayList = new ArrayList();
  public void add(Object object){
    this.arrayList.add(object);
  }
  
  public Iterator iterator(){
    return new ConcreteIterator(this.arrayList);
  }
  public void remove(){}
}