在 Java 中调用另一个类中的 ArrayList 的方法

Question

如果我有三门课。一类A，一类Customer，我在构造函数中放置了A 的ArrayList，还有一类SavingsAccount，我想将它们放在一起。在课堂上A 我有一个方法，我想从SavingsAccount 调用。我怎么做？并同时呼叫Customer 和SavingsAccount？ 在Customer 中有一个变量； SocSecNr，必须匹配SavingsAccount 中的Nr，才能在A 中正确，这就是为什么我将SavingsAccount 的ArrayList 放在Customer 中。 （这只是一个示例类。我只想知道如何在没有继承的情况下进行此调用）

import java.util.ArrayList;

public class A {
private ArrayList<Customer> customerlist;
private SavingsAccount account;

public A() {
    customerlist = new ArrayList<Customer>();
    account = new SavingsAccount();
}

public boolean deposit(long pNr, int accountId, double amount)
{   
    for(int i = 0; i < customerlist.size(); i++)
    {
        if(customerlist.get(i).getPCode() == pNr)
        {
            account.transaction(amount);
        }        
    }
    return false;        
       
}
public double transaction(){

    if(amount < 0 && balance + amount < 0)
        return -0;
    else
        return balance += amount;
}




   public class Customer {
private long pNr;
private ArrayList<SavingsAccount> accounts;

public Customer(long pCode)
{
    pNr = pCode;
    accounts = new ArrayList<SavingsAccount>();
}

public ArrayList<SavingsAccount> getAccount(){
    return accounts;
}
}



public class SavingsAccount {
private double balance;

public SavingsAccount(){
    accountId = accountCount;
}

public double transaction(double amount){
    if(amount < 0 && balance + amount < 0)
        return -0;
    else
        return balance += amount;

}
}

Answer 1

你可以通过两种方式实现它

1- 继承

class C extentds A{
 //all the public or protected attribues and methods are availble here 
} 

2- By 有关系。

class C{

   private A aType;

   aType.methode();
}

Answer 2

在 A 类中，我有一个我想从 C 调用的方法

您应该通过将C 字段放入A 来在A 和C 之间建立关联。您可以在构造函数中传递对它的引用或使用 setter 方法对其进行初始化。实际上，deposit 方法的代码中不需要它们，但您可以在此方法中初始化它们，以便进一步引用或在其他方法中使用。

编辑：

import java.util.ArrayList;

public class A {
  private ArrayList<Customer> customerlist;
  private Customer customer;
  private SavingsAccount account;

  public A() {
      customerlist = new ArrayList<Customer>();
  }

  public boolean deposit(long pNr, int accountId, double amount)
  {   
      for(Customer customer : customerlist) {
          if(customer.getPCode() == pNr) {
            this.customer = customer; //initialize
            List<SavingsAccount> accounts = customer.getAccounts();
            for (SavingsAccount account : accounts) {
              if (account.getAccountId() == accountId){
                this.account = account; //initialize
                account.transaction(amount);
                return true;
              } 
            }
          }        
      }
      return false;            
  }

}

public class Customer {
  private long pNr;
  private ArrayList<SavingsAccount> accounts;

  public long getPCode(){
    return pNr;
  }

  public Customer(long pCode)
  {
    pNr = pCode;
    accounts = new ArrayList<SavingsAccount>();
  }

  public ArrayList<SavingsAccount> getAccounts(){
    return accounts;
  }
}



public class SavingsAccount {
  private double balance;
  private int accountId;

  public int getAccountId(){
    return accountId;
  }

  public SavingsAccount(int accountId){
    this.accountId = accountId;
  }

  public double transaction(double amount){
    if(amount < 0 && balance + amount < 0)
        return -0;
    else
        return balance += amount;

  }
}