Extract Method

class Account
{
    public static void closeAcct()
    {
	int account;
	account = chooseAccount();

	if (account == -1)
	    return;

	if (acctActive[account] == false)
	    System.out.println("Account is not active.");

	else if (acctActive[account] == true)
...
    }

    public static void openAcct()
    {
	int account;
	account = chooseAccount();

	if (account == -1)
	    return;

	if (acctActive[account] == true)
...
    }

... // same for: doDeposit(), doWithdrawl(), and showBalance()
}

class Account
{
    public static boolean isAccountActive(int account)
    {
	if((account >= 0) && (account < acct.length))
	    return acctActive[account];
	else
	    throw new IllegalArgumentException("Invalid Account");
    }

    public static void closeAcct(int account)
    {
	if (isAccountActive(account) == false)
...
    }
    
    public static void openAcct(int account)
    {
	if (isAccountActive(account) == true)
...
    }
... // etcetera
}