清华大学：JAVA教学课件：5-11

程序5-12
abstract class ObjectStorage{
int objectnum=0;
Object storage[] = new Object[100];
abstract void put(Object o); //注意,没有大括弧("{}")
abstract Object get();
}
class Stack extends ObjectStorage{
private int point=0;
public void put(Object o){
storage[point++]=o;
objectnum++;
}
public Object get(){
objectnum--;
return storage[--point];
}
}
class Queue extends ObjectStorage{
private int top=0;
private int bottom=0;
public void put(Object o){
storage[top++]=o;
objectnum++;
}
public Object get(){
objectnum--;
return storage[bottom++];
}
}