观察者模式最佳案例实现[JAVA]

/**
* American Stock Exchange market(ASE) has a list of stocks.A stock object has two perspective information,symbol and price.

* Class StockMarket is a class that represents the stock market.

* Its constructor generates a collection of stocks using random numbers to build 3-letter stock symbols and random numbers for initial stock price.

* Implement a Java application when the stock price has been changed,all those investors who are interested in the stock market will be notified by receiving the most recent price.

* Create a driver class to test your implementation.
*
*/

package com.v5ent.rapid4j.pattern;

import java.util.ArrayList;
import java.util.List;
import java.util.Observable;
import java.util.Observer;
import java.util.Random;

/**
 * American Stock Exchange market(ASE) has a list of stocks.A stock object has two perspective information,symbol and price.

 * Class StockMarket is a class that represents the stock market.

 * Its constructor generates a collection of stocks using random numbers to build 3-letter stock symbols and random numbers for initial stock price.

 * Implement a Java application when the stock price has been changed,all those investors who are interested in the stock market will be notified by receiving the most recent price.

 * Create a driver class to test your implementation.
 * @author Mignet
 *
 */
public class StockTest {
    public static void main(String[] args) {
        StockMarket market = new StockMarket(10);
        market.show();
        market.invest();
        market.shuffle();
        market.show();
    }
}

class StockMarket{
    private List list;
    private int capacity;
    public StockMarket(int capacity){
        this.capacity=capacity;
        init(this.capacity);
    }
    private  List init(int n){
        list= new ArrayList();
        for(int i=0;i