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。