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。
package com.lyz.design.iterator;
/**
* Iterator
* @author binghe
*
*/
public interface Iterator {
Object next();
void first();
void last();
boolean hasNext();
}
package com.lyz.design.iterator;
/**
* ConcreteIterator
* @author binghe
*
*/
public 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();
}
}
package com.lyz.design.iterator;
/**
* Aggregate
* @author binghe
*
*/
public interface List {
Iterator iterator();
Object get(int index);
int getSize();
void add(Object obj);
}
package com.lyz.design.iterator;
/**
* ConcreteAggregate
* @author binghe
*
*/
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++;
}
}
package com.lyz.design.iterator;
/**
* Test
* @author binghe
*
*/
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));
}
}
}
a
b
c
=====
a
b
c