2

所以我在使用 Java 代码时遇到了很多困难，我应该修改 ContactList.java 以便它循环提示用户输入整数键。如果键为非负数，则在数组中搜索具有该键的 Person。如果找到此人，则显示此人。如果找不到 Person，则显示一条消息。如果用户输入否定键，程序应该终止。但不确定在哪里实现 while 循环。目前 run() 也会抛出 IOException。我正在尝试更改 run() 以使其捕获 IOException，如果捕获到异常，则显示描述性消息并终止。

import java.io.IOException;
import java.net.URL;
import java.util.Scanner;

public class ContactList {

    private Person[] theList;
    private int n;            // the number of Persons in theList

    // Returns a Scanner associated with a specific text-based URL
    // online.
    private Scanner makeScanner() throws IOException {
        final String source = 
          "http://userpages.umbc.edu/~jmartens/courses/is247/hw/05/05.txt";
        final URL src = new URL(source);
        return new Scanner(src.openStream());
    } // makeScanner()


    // Return a Person instance based upon data read from the given
    // Scanner.
    private Person getPerson(final Scanner in) throws FileFormatException {
        if (!in.hasNextLine())
          return null;

        String line = in.nextLine().trim();
        int key = Integer.parseInt(line);
        String name = in.nextLine().trim();
        String mail = in.nextLine().trim().toLowerCase();
        if (in.hasNextLine()) {
          String empty = in.nextLine().trim(); // skip blank line
          if (empty.length() > 0)
            throw new FileFormatException("missing blank line");
        } // if

        return new Person(key, name, mail);
    } // getPerson()


    // Display the array contents.
    private void display() {
        for (int i = 0; i < n; ++i)
          System.out.println(theList[i]);
    } // display()


    // Example code to display the contents of the contact list file.
    private void run() throws IOException {
        theList = new Person[1024];
        Scanner in = makeScanner();

        int index = 0; 
        Person p = getPerson(in);
        while (p != null) {
          theList[index++] = p;
          p = getPerson(in);
        }
        n = index;

        display();
    } // run()


    public static void main(String[] args) throws IOException {
        ContactList cl = new ContactList();
        cl.run();
    } // main()

} // class ContactList
4

2 回答 2

0

在方法中读取整个列表后，您可以放置​​它run()：

  private void run() throws IOException {
    theList = new Person[1024];
    Scanner in = makeScanner();

    int index = 0; 
    Person p = getPerson(in);
    while (p != null) {
      theList[index++] = p;
      p = getPerson(in);
    }
    n = index;

    display();

    int key = 0;
    do {
      System.out.print("Enter a key: ");
      try {
        Scanner userInput = new Scanner(System.in);
        key = userInput.nextInt();
      } catch (InputMismatchException e) {
        System.out.println("> Invalid key");
        continue;
      }

      Person found = search(key);
      if (found == null)
        System.out.println("> Person not found");
      else
        System.out.println("> Person found => " + found);
    } while(key >= 0);
  } // run()

该search方法是一个简单的循环，将列表中每个的 idPerson与提供的键进行比较。

对于run不抛出的方法IOException，请按照小册子的答案。

于 2012-05-02T17:22:40.553 回答
0

你知道try/catch吗？

private void run() {
    try {
        // Loop, etc.
    } catch (IOException e) {
        // Handle exception
    }
}
于 2012-05-02T16:23:04.643 回答