我想使用我創建的方法find()來搜索泛型類型T的arrayList元素。搜索時,用戶必須將它們正在搜索的項目for和兩個索引,他們希望在startPosition和endPosition之間進行搜索。每當我運行main()時,它總是打印-1,即使在我的測試代碼中,Chevy顯然是在0到3之間。誰能幫我弄清楚爲什麼它沒有印刷雪佛蘭所在的適當指數?謝謝!在Java中的兩個arrayList索引之間搜索泛型項目
ALIST:
import java.util.Scanner;
public class AList<T> implements ListInterface<T>
{
private T[] L;
private T k;
private int count;
public AList(int s)
{
L =(T[]) new Object[s];//Allows the client to decide the length of the list ASK HOW TO MAKE IT A SET SIZE OF 20
count = 0;
}//end of constructor
public void add(T item)throws ListException
{
if(count == L.length)
throw new ListException("Cannot add. List is full.");
if(item == null || item == "")
throw new ListException("Error. Unable to add. Cannot add null entries.");
L[count] = item;
count++;
}//end of add method
public void add(T item, int position)throws ListException
{
if(count == 0)
throw new ListException("Error. Unable to insert. List is empty.");
if(count == L.length)
throw new ListException("Error. Unable to insert. List is full");
if(item == null || item == "")
throw new ListException("Error. Unable to insert. Attempt to insert null object.");
if(position <= 0 || position > count)
throw new ListException("Error. Unable to insert. Bad position.");
for(int k = count-1; k >= position-1; k--)
{
L[k+1] = L[k];
L[2] = L[1];
}
L[position-1] = item;
count++;
}//end of insert method
public T get(int position)throws ListException
{
if(position <= 0 || position > count)
throw new ListException("Error. Unable to get. Bad position.");
if(count == 0)
throw new ListException("Error. Unable to get. List is empty.");
return L[position-1];
}// End of get method
public T set(T item, int position)throws ListException
{
if(item == null || item == "")
throw new ListException("Error. Unable to replace. Replacement cannot be null.");
if(position <= 0 || position > count)
throw new ListException("Error. Unable to replace. Bad position.");
if(count == 0)
throw new ListException("Error. Unable to replace. List is empty.");
T temp = L[position-1];
L[position-1] = item;
temp = item;
return temp;
}// End of set method
public int find(T item, int startPosition, int endPosition)throws ListException
{
if(startPosition < 0 || endPosition > count)
throw new ListException("Error. Unable to find. Start and/or end position bad.");
int found;
if(startPosition > endPosition)
found = -1;
else if(item.equals(L[startPosition]))
found = startPosition;
else
found = find(item, startPosition+1, endPosition);
return found;
}//method for finding
public int size()
{
return count;
}// End of size method
public String toString()
{
int k;
if(count == 0)
return "The list is empty. \n";
String temp = "";
for(k = 0; k < count; k++)
{
temp += L[k] += "\n";
}
return temp;
}//end of method toString
public T remove(int position)throws ListException
{
if(count == 0)
throw new ListException("Error. Unable to remove. List is empty.");
if(position <= 1 || position >= count)
throw new ListException("Error. Unable to remove. Bad position.");
T temp = L[position-1];
int k;
for(k = position-1; k <= count; k++)
{
L[k] = L[k+1];
}
count--;
return temp;
}//end of remove method
public void clear()
{
for(int k = count; k > 0; k--)
{
count--;
}
}// End of clear method
public boolean isEmpty()
{
if(L.length == 0)
return true;
else
return false;
}// End of isEmpty method
} //程序結束
測試代碼:
public static void main(String[] args)
{
try
{
AList<String> carList = new AList<String>(20);
carList.add("Ford");
carList.add("Chevy");
carList.add("Toyota");
carList.add("Mercedes");
System.out.println(carList);
System.out.println(carList.find("Chevy", 0, 3));
}
catch(ListException e)
{
System.out.println(e);
}
}
ListInterface:
public interface ListInterface<T>
{
public void add(T item)throws ListException;
public void add(T item, int position)throws ListException;
public T get(int position)throws ListException;
public T set(T item, int position)throws ListException;
public int find(T item, int startPosition, int endPosition);
public int size();
public T remove(int position) throws ListException;
public void clear();
public boolean isEmpty();
}
請出示你的'AList'類的其餘部分。您發佈的代碼(修復錯字之後)似乎不是您問題的根源。 – Eran
包括所有的AList和與之相伴的界面。如果你需要異常類,請告訴我。我很茫然,並且嘗試了一切,所以我非常感謝他們的幫助。 – Fall0ut