我正在做一项关于java中继承的家庭作业。我有点麻烦了解如何从子类访问超类中的数组。我看了几个其他的问题，因为我对java很新，我还是不太了解它。
这是超级
import java.text.NumberFormat;
/**
* Bank represents a single Bank containing a number of BankAccounts.
*/
public class Bank {
// Member variables:
/** The array of BankAccount objects contained in this bank. */
protected BankAccount[] myAccounts = new BankAccount[2000];
/** The number of BankAccount objects stored in the array in this bank. */
protected int numberOfAccounts = 0;
// Constructors:
/**
* Creates a Bank.
*/
public Bank() {}
// Methods:
/**
* Creates an account with the name and balance, and adds it to
* the bank's list of accounts.
* If the name already exists, no account will be created.
* @param aName The name for the new account.
* @param aBalance The initial balance for the new account.
*/
public void createAccount( String aName, double aBalance) {
BankAccount existing = this.findAccount( aName);
if( existing != null) return;
BankAccount anAccount = new BankAccount( aBalance, aName);
this.myAccounts[ numberOfAccounts] = anAccount;
this.numberOfAccounts++;
}
/**
* Finds an account in the bank's list of accounts by name.
* If no account is found, this method returns null.
* @param aName The name of the BankAccount to search for.
* @return The BankAccount bearing the given name, if found.
*/
public BankAccount findAccount( String aName) {
BankAccount answer = null;
for( int index = 0; index < numberOfAccounts; index++) {
BankAccount anAccount = this.myAccounts[ index];
if( aName.equals( anAccount.getName())) {
return( anAccount);
}
}
return( answer);
}
/**
* Returns a String which represents a short summary of
* all the accounts in the bank.
* @return A String representation of all accounts and their balances in the bank.
*/
public String toString() {
String answer = "";
NumberFormat currencyFormatter = NumberFormat.getCurrencyInstance();
for( int index = 0; index < numberOfAccounts; index++) {
BankAccount anAccount = this.myAccounts[ index];
String money = currencyFormatter.format( anAccount.getBalance());
answer += anAccount.getName() + " \t" + money + "\n";
}
return( answer);
}
}
这是子类的开头
public class BankSubClass extends Bank{
private double interestPaid;
// Constructor
public BankSubClass(String aName, double aBalance, double aInterest) {
super();
this.interestPaid = aInterest;
}
// Getters
public double getInterestPaid() {return(this.interestPaid);}
// Setters
public void setInterestPaid(double setInterestPaid) {this.interestPaid = setInterestPaid;}
// Other methods
public double endOfYear() {
for (i=0;i<BankAccount.length();i++) {
}
}
}
最后的循环是事情变得有点绊倒的地方。 Netbeans正在抛出错误，上面写着“找不到符号：变量i”。也许这与我试图使用的银行账户数据无关，我不知道。非常感谢任何帮助
谢谢你的时间！
修改的
所以这是同一作业的延续
感谢大家的回复，你的建议解决了这个问题，但我目前正在进行另一次减速。 for循环所在的这个方法背后的想法是运行BankAccount对象数组，检查它们是否属于InterestAccount类型（我之前构建的类），如果是，则调用annualUpdate（）该类的方法
这是InterestAccount类
public class InterestAccount extends BankAccount {
private double interestRate;
// Constructor
/**
* Create and interest bearing bank account with a balance, name,
* and interest rate
* @param aBalance The balance of the account
* @param aName The name tied to the account
* @param myInterestRate The interest rate of the account
*/
public InterestAccount(double aBalance, String aName, double myInterestRate) {
super(aBalance, aName);
this.interestRate = myInterestRate;
}
// Getters
/**
* Gets the interest rate of the account
* @return the interest rate of the account
*/
public double getInterestRate() {return(this.interestRate);}
// Setters
/**
* Sets the interest rate of the account
* @param interestSet The new interest rate of the account
*/
public void setInterestRate(int interestSet) {this.interestRate = interestSet;}
// Other Methods
/**
* Calculates the interest earned on the account over a year
* @return the interest earned over a year
*/
public double yearlyUpdate() {
double answer = (super.getBalance()*this.interestRate);
return answer;
}
}
这是我目前正在使用的超级课程
import java.text.NumberFormat;
/**
* Bank represents a single Bank containing a number of BankAccounts.
*/
public class Bank {
// Member variables:
/** The array of BankAccount objects contained in this bank. */
protected BankAccount[] myAccounts = new BankAccount[2000];
/** The number of BankAccount objects stored in the array in this bank. */
protected int numberOfAccounts = 0;
// Constructors:
/**
* Creates a Bank.
*/
public Bank() {}
// Methods:
/**
* Creates an account with the name and balance, and adds it to
* the bank's list of accounts.
* If the name already exists, no account will be created.
* @param aName The name for the new account.
* @param aBalance The initial balance for the new account.
*/
public void createAccount( String aName, double aBalance) {
BankAccount existing = this.findAccount( aName);
if( existing != null) return;
BankAccount anAccount = new BankAccount( aBalance, aName);
this.myAccounts[ numberOfAccounts] = anAccount;
this.numberOfAccounts++;
}
/**
* Finds an account in the bank's list of accounts by name.
* If no account is found, this method returns null.
* @param aName The name of the BankAccount to search for.
* @return The BankAccount bearing the given name, if found.
*/
public BankAccount findAccount( String aName) {
BankAccount answer = null;
for( int index = 0; index < numberOfAccounts; index++) {
BankAccount anAccount = this.myAccounts[ index];
if( aName.equals( anAccount.getName())) {
return( anAccount);
}
}
return( answer);
}
/**
* Returns a String which represents a short summary of
* all the accounts in the bank.
* @return A String representation of all accounts and their balances in the bank.
*/
public String toString() {
String answer = "";
NumberFormat currencyFormatter = NumberFormat.getCurrencyInstance();
for( int index = 0; index < numberOfAccounts; index++) {
BankAccount anAccount = this.myAccounts[ index];
String money = currencyFormatter.format( anAccount.getBalance());
answer += anAccount.getName() + " \t" + money + "\n";
}
return( answer);
}
}
最后，这里是我试图为循环
运行它的子类public class BankSubClass extends Bank{
private double interestPaid;
// Constructor
public BankSubClass(String aName, double aBalance, double aInterest) {
super();
this.interestPaid = aInterest;
}
// Getters
public double getInterestPaid() {return(this.interestPaid);}
// Setters
public void setInterestPaid(double setInterestPaid) {this.interestPaid = setInterestPaid;}
// Other methods
public double endOfYear() {
double trackInterest=0;
for (int i=0;i<numberOfAccounts;i++) {
BankAccount working = myAccounts[i];
boolean hasInterest = working instanceof InterestAccount;
if (hasInterest) {
trackInterest = trackInterest + working.yearlyUpdate();
}
return trackInterest;
}
}
}
目前netbeans尝试在“工作”上调用它时找不到“annualUpdate（）”方法我不理解的是因为前面的代码验证了工作对象属于InterestAccount类型，它应该有那种方法可用
感谢您的帮助！
答案 0 :(得分：1)
// Other methods
public double endOfYear() {
for (i=0;i<BankAccount.length();i++) {
}
}
您需要声明i
// Other methods
public double endOfYear() {
for (int i=0;i<BankAccount.length();i++) {
}
}
答案 1 :(得分：0)
就像错误一样：我未定义。
尝试：
for (int i=0;i<BankAccount.length();i++)
我猜这仍然很糟糕，因为你想要数组的长度，而不是BankAccount类（可能是未定义的）
for (int i=0;i<myAccounts.length();i++)
答案 2 :(得分：0)
对于错误，您需要在BankSubClass.endOfYear中使用它之前定义变量i。声明应该是
for (int i=0;i<BankAccount.length();i++)
答案 3 :(得分：0)
你没有在for循环中声明i
for (int i=0;i<BankAccount.length();i++)
答案 4 :(得分：0)
在你的循环中，变量i是未声明的。此外，由于我认为您希望遍历数组中的帐户，我认为您应该使用以下内容：
for(int i = 0; < numberOfAccounts; i++)
{
BankAccount bankAccount = myAccounts[i];
// other stuff
}