Java基础之集合框架——使用集合Vector<>挑选演员（TryVector）

控制台程序。

 public class Person implements Comparable<Person> {
   // Constructor
   public Person(String firstName, String surname) {
     this.firstName = firstName;
     this.surname = surname;
   }
 
   @Override
   public String toString() {
     return firstName + " " + surname;
   }
 
   // Compare Person objects
   public int compareTo(Person person) {
     int result = surname.compareTo(person.surname);
     return result == 0 ? firstName.compareTo(person.firstName) : result;
   }
 
   private String firstName;            // First name of person
   private String surname;              // Second name of person
 }

使用sort()方法对列表排序时，必须通过某种方式确定列表中对象的顺序。最合适的方式就是在Person类中实现Comparable<>接口。Comparable<>只声明了comparableTo()方法。

如果集合中存储的对象的类型实现了Comparable<>接口，就可以把集合对象作为参数传送给sort()方法。

 import java.util.Vector;
 import java.util.ListIterator;
 import java.util.Collections;
 import java.io.*;
 
 public class TryVector {
   public static void main(String[] args) {
     Person aPerson = null;                                             // A person object
     Vector<Person> filmCast = new Vector<>();
 
     // Populate the film cast
     while(true) {                                                      // Indefinite loop
       aPerson = readPerson();                                          // Read in a film star
       if(aPerson == null) {                                            // If null obtained...
         break;                                                         // We are done...
       }
       filmCast.add(aPerson);                                           // Otherwise, add to the cast
     }
 
     int count = filmCast.size();
     System.out.println("You added " + count + (count == 1 ? " person":  " people") + " to the cast:");
     // Show who is in the cast using an iterator
     ListIterator<Person> thisLot = filmCast.listIterator();
 
     while(thisLot.hasNext()) {       // Output all elements
       System.out.println( thisLot.next());
     }
     System.out.println("\nThe vector currently has room for " + (filmCast.capacity() - count) + " more people.");
 
     // Now sort the vector contents and list it
     Collections.sort(filmCast);
     System.out.println("\nThe cast in ascending sequence is:");
     for(Person person : filmCast) {
       System.out.println(person);
     }
   }
 
   // Read a person from the keyboard
   static Person readPerson() {
     // Read in the first name and remove blanks front and back
     String firstName = null;
     String surname = null;
     System.out.println("\nEnter first name or ! to end:");
     try {
       firstName = keyboard.readLine().trim();                          // Read and trim a string
 
       if(firstName.charAt(0) == '!') {                                 // Check for ! entered
         return null;                                                   // If so, we are done...
       }
 
       // Read in the surname, also trimming blanks
       System.out.println("Enter surname:");
       surname = keyboard.readLine().trim();                            // Read and trim a string
     } catch(IOException e) {
       System.err.println("Error reading a name.");
       e.printStackTrace();
       System.exit(1);
     }
     return new Person(firstName,surname);
   }
 
   static BufferedReader keyboard = new BufferedReader(new InputStreamReader(System.in));
 }

把filmCast对象传送给Collections类的sort()静态方法，就会导致对集合中的对象排序。

键盘对象是InputStreamReader对象中封装的System.in，而InputStreamReader对象封装在BufferedReader对象中。InputStreamReader对象可以把输入从字节流System.in转换为字符。BufferedReader对象缓存了从InputStreamReader读入的数据。因为输入包含一系列字符串，而每个字符串占一行，所以readLine()方法可以完成我们需要的工作。