为什么我不能使用我之前在 class 中创建的数组来打印出 phone 一本书的编号？

Question

我正在尝试为学校项目制作 phone 一本书 reader。该程序要求输入名字和姓氏。姓名和 phone 人数存储在一个数组中。如果您不输入名字，而姓氏分配给多个人，程序应该会吐出多个人的 phone 号码。抱歉，可能有点长。

public static void main(String[] args) {

    //Where the user input starts, gotta get dat number
    Scanner scan = new Scanner(System.in);

    System.out.print("First Name? ");
    String first = scan.nextLine();

    System.out.print("Last Name? ");
    String last = scan.nextLine();

    String fullname = first + last;

    int[] count = new int[0];
    int counter=0;

    if(first.equals("quit") || last.equals("quit"))
        System.out.println("Bye");
    else
    {
        for(int l=0; l < 5; l++)
        {
            PhoneBook pb = new PhoneBook();
            PhoneEntry entry = pb.search(fullname);
            if( entry != null)
            {
                count[counter] = l; //this is where the issue lies
                counter++;
            }
        }

    }

    if(count.length != 0)
    {
        for(int x=0; x<count.length; x++ )
        {
            PhoneBook pb = new PhoneBook();
            System.out.println("Name: " + pb.phoneBook[count[x]].name + " Number: " + pb.phoneBook[count[x]].phone);
            x++;
        }
    }
}

class PhoneEntry
{
    String name;    // name of a person
    String phone;   // their phone number
    PhoneEntry( String n, String p )
    {
        name = n; phone = p;
    }
}

class PhoneBook
{ 
    PhoneEntry[] phoneBook; 
    PhoneBook()    // constructor
    {
        phoneBook = new PhoneEntry[ 5 ] ;
        phoneBook[0] = new PhoneEntry( "James Barclay", "(418)665-1223" ); 
        phoneBook[1] = new PhoneEntry( "Grace Dunbar",  "(860)399-3044" );
        phoneBook[2] = new PhoneEntry( "Paul Kratides", "(815)439-9271" );
        phoneBook[3] = new PhoneEntry( "Violet Smith",  "(312)223-1937" );
        phoneBook[4] = new PhoneEntry( "John Smith",     "(913)883-2874" );
    }

    PhoneEntry search( String targetName )  
    {
        for (int j=0; j<phoneBook.length; j++)
        {
            if ( phoneBook[ j ].

                    //stuff is to make it so that it only tests if its to upper case and if it contains the target
                    name.toUpperCase().contains( targetName.toUpperCase()))
                return phoneBook[ j ];
        }
        return null;
    }
}

非常感谢任何帮助。

Answer 1

您写道：

 count[counter] = l; //this is where the issue lies

其实真正的问题在于：

 int[] count = new int[0];

您已经创建了大小为零的数组；也就是说，你不能将任何元素放入到。如果您尝试这样做，您将得到一个例外。大概这就是正在发生的事情......

在Java中，数组的大小是固定的。您以给定的大小创建它们，并且它们将永远保持该大小。

为什么我不能使用我之前在 class 中创建的数组来打印出 phone 一本书的编号？

Why can't I use the array I made in a class earlier to print out the numbers for a phone book?

java

arrays

class

operators