以银行帐户类BankAccount作为超类，创建一个支票帐户类CheckingAccount。

以银行帐户类BankAccount作为超类，创建一个支票帐户类CheckingAccount。

要求：

1．增加一个表示交易数量的实例变量transactionCount

2．增加一个新方法deductFees，表示从帐户中扣除一定税款的操作，具体规则为交税时若交易数量超过3笔，超出的每笔交易扣除2元税款

3．提示：必要的话需要覆盖存、取款的方法

public class BankAccount {
	
	private String id;
	private double balance;
	
	public BankAccount(String id)
	{
		this.id = id;
	}
	
	public void deposit(double amount)
	{
		balance += amount;
	}
	
	public void withdraw(double amount)
	{
		balance -= amount;
	}
	
	public String getId()
	{
		return id;
	}
	
	public double getBalance()
	{
		return balance;
	}
	

}

public class CheckingAccount extends BankAccount{
	
	private int transactionCount;
	
	public CheckingAccount(String id)
	{
		super(id);
	}
	
	public void deposit(double amount)
	{
		super.deposit(amount);
		transactionCount++;
	}
	
	public void withdraw(double amount)
	{
		super.withdraw(amount);
		transactionCount++;
	}
	
	public void deductFees()
	{
		if(transactionCount>3){
			double i = (transactionCount - 3)*2;
			super.withdraw(i);
		}
		transactionCount = 0;
	}
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		CheckingAccount account = new CheckingAccount("B0001");
		account.deposit(1000);
		account.deposit(1000);
		account.deposit(1000);
		account.deposit(1000);
		account.withdraw(1000);
		account.withdraw(1000);
		account.deductFees();
		System.out.println(account.getBalance());
		System.out.println(account.transactionCount);

	}
}