如果 String .contains 方法不适合，如何 return null？

Question

我有此代码，如果没有标题包含 wordInTitle 的书，或者如果 wordInTitle 为 null 或“”，我想 return null。我可以设法为 null 和 "" 做到这一点，但如果没有包含 wordInTitle 的书则不行。有人可以帮我吗？

public String[] getBookTitlesContaining(String wordInTitle)
{
    int nBooks = 0;
    String[] bookTitle = new String[nBooks];

    for (Book booksTitles : inventory)
    {
        if(booksTitles.getTitle().toLowerCase().contains(wordInTitle.toLowerCase()))
        {
            nBooks++;
        }
    }

    int titleB = 0;
    bookTitle = new String[nBooks];

    for (Book booksTitles : inventory)
    {
        if(booksTitles.getTitle().toLowerCase().contains(wordInTitle.toLowerCase()))
        {
            bookTitle [titleB] = booksTitles.getTitle();
            titleB++;
        }
    }

    if ((wordInTitle == null) || (wordInTitle == "")) 
    {
        return null;
    }

    return bookTitle;

提前致谢

Answer 1

统计有书名的书籍数量后，如果计数为0，则可以return null;

public String[] getBookTitlesContaining(String wordInTitle)
{
    int nBooks = 0;
    String[] bookTitle = new String[nBooks];

    for (Book booksTitles : inventory)
    {
        if(booksTitles.getTitle().toLowerCase().contains(wordInTitle.toLowerCase()))
        {
            nBooks++;
        }
    }

    if (nBooks == 0) return null;

Answer 2

更改此 if 以包括没有匹配图书的情况：

if ((wordInTitle == null) || (wordInTitle == "") || (nBooks == 0)) 
{
    return null;
}

如果 String .contains 方法不适合，如何 return null？

How to return null if String .contains method doesn't fit?

java

null

contains