迭代模式

迭代模式：给定一个语言，定义它的文法的一种表示，并定义一个解释器，这个解释器使用该表示来解释语言中的句子。以下是例子:

public interface Iterator {  

Object next();

void first();

void last();

boolean hasNext(); }

 

public class IteratorImpl implements Iterator{

private List list; private int index;

public IteratorImpl(List list){

index = 0;

this.list = list; }

public Object next() {

Object obj = list.get(index);

index++; return obj; }

public void first() {

index = 0; }

public void last() {

index = list.getSize(); }

public boolean hasNext() {

return index < list.getSize(); } }

 

public interface List {

Iterator iterator();

Object get(int index);

int getSize();

void add(Object obj);

}

 

public 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++; } }

 

//测试类

public class Test {

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)); } } }