用java写一个程序。用对象模拟实现一个售货过程。

好的，下面是一个简单的示例程序，模拟一个售货过程：

import java.util.ArrayList;

public class VendingMachine {
    private ArrayList<Product> products;
    private float balance;
    
    public VendingMachine() {
        products = new ArrayList<>();
        balance = 0;
    }
    
    public void addProduct(Product product) {
        products.add(product);
    }
    
    public void insertCoin(float amount) {
        balance += amount;
    }
    
    public void purchase(int productIndex) {
        Product product = products.get(productIndex);
        if (balance >= product.getPrice()) {
            System.out.println("Dispensing " + product.getName());
            balance -= product.getPrice();
        } else {
            System.out.println("Not enough balance");
        }
    }
    
    public void displayProducts() {
        for (int i = 0; i < products.size(); i++) {
            Product product = products.get(i);
            System.out.println(i + ": " + product.getName() + " - " + product.getPrice());
        }
    }
    
    public float getBalance() {
        return balance;
    }
}

public class Product {
    private String name;
    private float price;
    
    public Product(String name, float price) {
        this.name = name;
        this.price = price;
    }
    
    public String getName() {
        return name;
    }
    
    public float getPrice() {
        return price;
    }
}

public class Main {
    public static void main(String[] args) {
        VendingMachine vendingMachine = new VendingMachine();
        vendingMachine.addProduct(new Product("Coke", 1.5f));
        vendingMachine.addProduct(new Product("Chips", 2.0f));
        vendingMachine.addProduct(new Product("Candy", 0.5f));
        
        vendingMachine.displayProducts();
        
        vendingMachine.insertCoin(1.0f);
        vendingMachine.purchase(0);
        
        vendingMachine.insertCoin(2.0f);
        vendingMachine.purchase(1);
        
        vendingMachine.insertCoin(1.0f);
        vendingMachine.purchase(2);
    }
}

程序中有三个类：VendingMachine、Product和Main。

VendingMachine类表示售货机，里面有一个产品列表和一个余额变量。其中，addProduct方法用于添加产品，insertCoin方法用于插入硬币，purchase方法用于购买产品，displayProducts方法用于显示产品列表，getBalance方法用于获取余额。

Product类表示产品，包含名称和价格两个属性。

Main类是程序的入口，创建一个VendingMachine对象并添加三个产品，然后插入硬币、购买产品并显示余额。