简单的OOPS演示，坚持for循环的功能及其在main方法中的作用

Question

关于这段代码的唯一信息是这个CreditCard类定义了模拟传统信用卡简化版本的信用卡对象。它们存储有关客户、发行银行、帐户标识符、信用额度和当前余额的信息。他们不收取利息或滞纳金，但他们限制会导致信用卡余额超过信用额度的费用。以下代码摘自《java中的数据结构和算法》一书:请帮助我了解for循环，它是:

for (int val = 1; val <= 16; val++) {  
     wallet[0].charge(3*val);
     wallet[1].charge(2*val);
     wallet[2].charge(val);
}

为什么充电方法有参数3val、2val和val。这个循环真正做什么？从以下代码：

package com.illustrations;

public class CreditCard{
    
    private String customer;
    private String bank;
    private String account;
    private int limit;
    protected double balance;

    public CreditCard(String customer, String bank, String account, int limit, double balance){     
        this.customer = customer;
        this.bank = bank;
        this.account = account;
        this.limit = limit;
        this.balance = balance;    
    }
    
    public CreditCard(String customer, String bank, String account, int limit) {
        this(customer, bank, account, limit, 0.0);
    }
    
    public String getCustomer(){ return customer; }
    public String getBank() { return bank; }
    public String getAccount() { return account; }
    public int getLimit() { return limit; }
    public double getBalance() { return balance; }

    public boolean charge(double price) {
        if(price + balance > limit)  
            return false;
        balance = balance + price; return true;
    }
    
    public void makePayment(double amount) {
        balance -=amount;
    }
     
    public static void printSummary(CreditCard card) {
        
        System.out.println("Customer ="+card.customer);
        System.out.println("Bank ="+card.bank);
        System.out.println("Account ="+card.account);
        System.out.println("Balance ="+card.balance);       
        System.out.println("Limit ="+card.limit);
    }
    
    public static void main(String[] args) {
        
         CreditCard[ ] wallet = new CreditCard[3];
         wallet[0] = new CreditCard("John Bowman", "California Savings", "5391 0375 9387 5309", 5000);
         wallet[1] = new CreditCard("John Bowman", "California Federal", "3485 0399 3395 1954", 3500);
         wallet[2] = new CreditCard("John Bowman", "California Finance", "5391 0375 9387 5309", 2500, 300);
        
         for (int val = 1; val <= 16; val++) {  
         wallet[0].charge(3*val);
         wallet[1].charge(2*val);
         wallet[2].charge(val);
         } 
         
         for (CreditCard card : wallet) {  
             CreditCard.printSummary(card); // calling static method
         
             while (card.getBalance() > 200.0) {  
                  card.makePayment(200);
                  System.out.println("New balance = " +card.getBalance());
             }
         
         }    
   }
}

Answer 1

我真的看不出有什么意义。事实上，定义了3种钱包——储蓄、联邦和金融，储蓄在剩下的两种钱包中信用额度最大。所以我们在3*val的for循环中做的是保持储蓄钱包中存钱的速度是金融钱包的三倍，因为它的限额要高得多。一旦达到限制，我们就不允许在钱包中添加更多的钱。