//Iterator

interface Iterator {

Object next();

void first();

void last();

boolean hasNext();

}

//ConcreteIterator

class IteratorImpl implements Iterator {

private List list;

private int index;

public IteratorImpl(List list) {

index = 0;

this.list = list;

}

public void first() {

index = 0;

}

public void last() {

index = list.getSize();

}

public Object next() {

Object obj = list.get(index);

index++;

return obj;

}

public boolean hasNext() {

return index < list.getSize();

}

}

//list

interface List {

Iterator iterator();

Object get(int index);

int getSize();

void add(Object obj);

}

//ConcreteAggregate

class ListImpl implements List {

private Object[] list;

private int index;

private int size;

public ListImpl() {

index = 0;

size = 0;

list = new Object[100];

}

public Iterator iterator() {

return new IteratorImpl(this);

}

public Object get(int index) {

return list[index];

}

public int getSize() {

return this.size;

}

public void add(Object obj) {

list[index++] = obj;

size++;

}

}

//

public class DS16_Iterator{

public static void main(String[] args) {

List list = new ListImpl();

list.add("a");

list.add("b");

list.add("c");

//第一种迭代方式

Iterator it = list.iterator();

while (it.hasNext()) {

System.out.println(it.next());

}

System.out.println("=====");

//第二种迭代方式

for (int i = 0; i < list.getSize(); i++) {

System.out.println(list.get(i));

}

}

}