我正在编写一个列表 ADT，与（堆栈和队列）不同，我将能够在列表中的任何位置添加/删除项目。我还希望能够遍历列表。所以我正在创建指针来跟踪项目。当我尝试在列表中添加项目（在测试工具类中）时，我得到一个绑定的不匹配。
请看一下下面的界面，我想您将能够获得更好的主意。
package List;
public interface ListInterface < ObjectType extends KeyInterface > extends Iterable<ObjectType> {
public void add ( ObjectType item ); // adds item in front of the key
public ObjectType remove ( ); // returns item at the key and removes it
public ObjectType get ( ); // returns item at the key
public boolean empty ( ); // returns boolean // check for empty
public int length ( ); // length of the list
public void toFront ( ); // moves pointer to the front of the list
public void advance( ); // moves the pointer to the next item
public void find ( String key ); // pointer finds the input key
public boolean offEnd ( ); // returns true if pointer is off the list
}
使用有界类型参数使 ObjectType 成为KeyInterface
下面的子类型是 KeyInterface
package List;
public interface KeyInterface {
public String getKey ( ); // Returns the Key of the item
}
这是我的 List 实现的样子。
package List;
import java.util.Iterator;
public class ListImplementation < ObjectType extends KeyInterface > implements ListInterface<ObjectType> {
ObjectType[] items; // the items in the list
int cursor; // the list cursor
int length; // the length of the list
public ListImplementation() {
this(100);
}// constructor
public ListImplementation(int size) {
items = (ObjectType[]) new KeyInterface[size];
cursor = 0;
length = 0;
}// constructor
@Override
public Iterator<ObjectType> iterator() {
return new ListIterator<ObjectType>(this);
}
@Override
public void add(ObjectType item) {
int j;
if ( length >= items.length ) {
throw new NullPointerException();
}
else {
for ( j = length-1 ; j>=cursor ; j-- ) {
items[j+1] = items[j];
}
items[cursor] = item;
length = length + 1;
}
}
@Override
public ObjectType remove() {
ObjectType i;
int j;
if ( cursor >= length ) {
throw new NullPointerException();
}
else {
i = items[cursor];
for ( j=cursor+1 ; j<length ; j++ ) {
items[j-1] = items[j];
};
length = length-1;
items[length] = null;
return i;
}
}
@Override
public ObjectType get() {
if ( cursor >= length ) {
throw new NullPointerException();
}
else {
return items[cursor];
}
}
@Override
public boolean empty() {
return length == 0;
}
@Override
public int length() {
return length;
}
@Override
public void toFront() {
cursor = 0;
}
@Override
public void advance() {
if ( cursor < length ) {
cursor = cursor + 1;
}
}
@Override
public void find(String key) {
while ( cursor < length && key.compareTo(items[cursor].getKey()) != 0 ) {
cursor = cursor + 1;
}
}
@Override
public boolean offEnd() {
return cursor >= length;
}
}
从逻辑上讲，我在这个类中看不到任何错误，并且我已经分别测试了这些方法。还制作了一个 List Iterator 类来遍历 List。这就是它的样子。
public class ListIterator<ObjectType extends KeyInterface > implements Iterator<ObjectType> {
private int cursor; // the cursor that iterates through the list
private ListImplementation <ObjectType> list; // the list being iterated over
ListIterator ( ListImplementation <ObjectType> l ) {
list = l;
cursor = 0;
}; // constructor
@Override
public boolean hasNext() {
return cursor < list.length;
}
@Override
public ObjectType next() {
ObjectType i;
if ( cursor >= list.length ) {
throw new NoSuchElementException();
}
else {
i = list.items[cursor];
cursor = cursor + 1;
return i;
}
}
@Override
public void remove() {
throw new UnsupportedOperationException(); // Doesn't do anything
}
}
我知道 remove 方法没有做任何事情，因为它的设计很糟糕，请暂时忽略它。现在我被困在测试线束部分。我不知道如何添加不同的项目，因为类中有很多扩展。
public static void main(String args[]){
ListImplementation < String> ls = new ListImplementation < String>();
}
无论我放在里面什么<>结果都是有界的不匹配。所以什么可以是有界参数的有效替代品。帮助？？