使用“ startsWith（）”進行字符串搜索

Question

在過去的兩天里，我一直在研究電子郵件目錄程序，在一種方法中，我試圖建立一個搜索功能，以根據用戶的字符輸入來搜索電子郵件。 我試圖使其遍歷到方法循環的位置，並且用戶一次在電子郵件中鍵入一個字符，直到為該方法構造的數組中只有一封電子郵件。

這是我的代碼：

private void searchContact()    
{
    String[] newRecords=new String[emailRecords.size()];        //temp array for searching
    ArrayList<String> searchRecords=new ArrayList<String>();    //to be passed to insertion sort
    newRecords=emailRecords.toArray(newRecords);                

    for(String Records: newRecords) 
    {
        Scanner search=new Scanner(System.in);                  //setup for user input
        String letter;
        String searchVal;

        System.out.println("Please enter the first letter of the email you're trying to find.");
        letter=search.nextLine();

        if (searchRecords.size()!=1)    
        {   
            for (int i=0; i<newRecords.length;i++)          //counter for indexes
            {
                searchVal=newRecords[i];                        //set temp value to set index

                if (searchVal.startsWith(letter))               //starts with boolean
                {
                    searchRecords.add(searchVal);               //add to temp array for later comparison
                }
            }
        }
        else    
        {
            break;                                              //break if one remains in the array.
        }
    }
    System.out.println(searchRecords);                          //TODO erase when finalizing
}

這是當我運行該程序輸入以相同字母開頭的名稱時發生的情況：

Please enter the number of your option choice:
1. Add a new contact
2. Search for an exsisting contact
3. Exit
1
Please enter the email adress.
mark
***mark was successfully stored.***
Please enter the number of your option choice:
1. Add a new contact
2. Search for an exsisting contact
3. Exit
1
Please enter the email adress.
mike
***mike was successfully stored.***
Please enter the number of your option choice:
1. Add a new contact
2. Search for an exsisting contact
3. Exit
1
Please enter the email adress.
molly
***molly was successfully stored.***
Please enter the number of your option choice:
1. Add a new contact
2. Search for an exsisting contact
3. Exit
2
Please enter the first letter of the email you're trying to find.
m
Please enter the first letter of the email you're trying to find.
a
Please enter the first letter of the email you're trying to find.
r
[mark, mike, molly]
Please enter the number of your option choice:
1. Add a new contact
2. Search for an exsisting contact
3. Exit

在輸入信息並嘗試通過輸入“ m”，“ a”，“ r”和“ k”來搜索“ mark”之后，這里是我的預期輸出：

Please enter the next letter of the email you're trying to find.
m
Please enter the next letter of the email you're trying to find.
a
Please enter the next letter of the email you're trying to find.
r
Please enter the next letter of the email you're trying to find.
k
[mark]

我試圖在另一個計數之外使用另一個for循環，並使用它來移動給定字符串的索引，但是失敗了。 我覺得我已經接近了，但可以俯瞰某些地方。 任何建議或策略將不勝感激！ 太感謝了。

Answer 1

假設emailRecords包含您所有的電子郵件，則您的任務是這樣的：

private void searchContact() {
    assert(!(emailRecords == null || emailRecords.isEmpty()));// :P
    //initially copy all
    ArrayList<String> searchRecords = new ArrayList<>(emailRecords);
    //prepare scanner
    Scanner search = new Scanner(System.in);
    //initialize query
    String query = "";
    //loop:
    while (searchRecords.size() > 1) {
        System.out.println("Please enter the first letter of the email you're trying to find.");
        //read from input
        query += search.nextLine();
        //iterate through remaining searchRecords
        for (Iterator<String> it = searchRecords.iterator(); it.hasNext();) {
            final String entry = it.next();
            if (!entry.startsWith(query)) {//...conditionally
                it.remove();//..remove (from searchRecords)
            }
        }
    }
    //print output - first/last of searchRecords
    if (!searchRecords.isEmpty())
        System.out.println(searchRecords.get(0));
    else
        System.out.println("No record found.");
}

Answer 2

您可能要嘗試的一件事是使用trie數據結構來存儲電子郵件地址。 來自http://en.wikipedia.org/wiki/Trie的 “ Trie的常見應用是存儲預想性文本或自動完成詞典...”。