返回一个字符串以供Super类的抽象方法显示

Question

The abstract method statement (in the super class) must be implemented to return a string representation of a statement.

So I've done the following:

 public abstract String statement(); //The abstract method in my super class

..and the method in my subclass:

//@Override
public String statement() 
{
    return String.format("Account no %d has balance R%d and minimum balance R%d", accountNumber,balance,getMinBalance());
}

My main class just calls the Account class (the super class in question) as follows:

new SavingsAccount(Integer.toString(ao[i]),ao[i+1],ao[a]); //ao being the array which contains the values.

However, the console just terminates without displaying anything (I'm also not familiar with implementation).

Here's the full code:

Main:

public class AccountList 
{
    public static void main(String[] args) 
    {
        int[] ao = {00000,0,0,12345,500,250,23456,230,-50,34567,340,500,45678,-320,-50,56789,-320,-500};

        for(int i=0;i<ao.length;i=i+3)
        {
            int a = i+2;
            if(ao[a]>=0)
            {

                new SavingsAccount(Integer.toString(ao[i]),ao[i+1],ao[a]);
            }
            if(ao[a]<=0)
            {

                new ChequeAccount(Integer.toString(ao[i]),ao[i+1],ao[a]);
            }   
        }
    }
}

Super class:

public abstract class Account implements InterestAccount
{
    static String accountNumber;
    int balance;

    public Account()
    {
        accountNumber = "00000";
        balance = 0;
        //statement();
    }
    public Account(String accountNumber,int balance)
    {
        setAccountNum(accountNumber);
        setBalance(balance);
    }
    public void setAccountNum(String accNum)
    {
        accountNumber = accNum;
    }
    public void setBalance(int balance)
    {
        this.balance = balance;
    }
    public String getAccountNumber()
    {
        return accountNumber;
    }
    public int getBalance()
    {
        return balance;
    }
     public abstract String statement();
}

One of the sub-classes:

public class SavingsAccount extends Account
{
    int minBalance;

    public SavingsAccount()
    {
        super();
        minBalance = 0;
    }
    public SavingsAccount(String accountNum,int minBalance,int balance)
    {
        super(accountNum,balance);
        setMinBalance(minBalance);
    }
    public void setMinBalance(int minBalance)
    {
        this.minBalance = minBalance;
    }
    public int getMinBalance()
    {
        return minBalance;
    }
    @Override
    public int calculateInterest(int value) {

        if(minBalance>balance)
        {
            return 0;           
        }
        else
        {
            return (minBalance*balance)/100;
        }
    }
    //@Override
    public String statement() 
    {
        return String.format("Account no %d has balance R%d and minimum balance R%d", accountNumber,balance,getMinBalance());
    }

}

Answer 1

You never calls the method statement.

1) create a new SavingsAccount object

new SavingsAccount(Integer.toString(ao[i]),ao[i+1],ao[a]);

2) Constructor class got call by above statement

public SavingsAccount(String accountNum,int minBalance,int balance)
{
    super(accountNum,balance);
    setMinBalance(minBalance);
}

3) Subclass then call superclass method public Account(String accountNumber,int balance) { setAccountNum(accountNumber); setBalance(balance); }

4) SetBalance is called

public void setBalance(int balance)
{
    this.balance = balance;
}

5) setMinBalance called

public void setMinBalance(int minBalance)
{
    this.minBalance = minBalance;
}

6) End of create object SavingsAccount

No single statement calling the method statement

Answer 2

It might help to know more of your code, but from what I see, there are some possible cases:

• Your code runs and terminates without an error. Reason you don't see anything is, there is nothing written to the standard output stream (eg via System.out.println()).
• Your code has some internal problems, which cause an exception, which again is not shown due to a broken logging mechanism.

In any case, use a debugger to step through you code and determine which parts run perfectly and if any fail. It might help to extract some local variables, give them proper meaningful names and watch their contents during execution.