如何将一个类中的变量值用于另一个类？

Question

I've defined a variable withdraw in class Account . It performs the withdrawl function just fine that's defined inside the Account class. However, I wish to access the value of withdraw variable inside the interest function present in the Sav_acct class. It's taking the value of withdraw as 0. How can I use the value of withdraw from the withdrawl function inside the interest function so I can perform the right mathematical operation?

public class Account {
    String customer_name;
    int account_number;
    String type_account;
    int balance = 2500;
    double deposit;

    public static double withdraw;

    void deposit() {
        Scanner sc = new Scanner(System.in);
        System.out.println("how much do you want to deposit?");
        int amo = sc.nextInt();
        deposit = balance + amo;

        System.out.println("Your current balance is " + balance);
    }

    void withdrawl() {
        Scanner sc = new Scanner(System.in);
        System.out.println("how much do you want to withdraw?");
        int amo = sc.nextInt();
        withdraw = balance - amo;
        if (withdraw < 0) {
            System.out.println("Your balance is insufficient");
        }
        else {
            System.out.println("Your current balance is " + withdraw);
        }
    }
}

class Curr_acct extends Account {

    @SuppressWarnings("empty-statement")
    void penalty() {
        double Service_charge = withdraw - 100;
        double falling = Service_charge;

        System.out.println("You've been charged" + " 100" + " due to low balance");
        System.out.println("Your current amount is " + falling);
    }
}

class Sav_acct extends Account {
    void interest() {
        double interest;
        interest = (1 % 100) * withdraw;
        double total_amount = interest + withdraw;
        System.out.println("Your new balance with interest is " + total_amount);
    }
}

class publish {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        System.out.println("Enter your name");
        String n = sc.nextLine();
        System.out.println("Enter your account type: Savings Account or Current Account");
        String t = sc.nextLine();
        if ("Savings Account".equals(t)) {
            System.out.println("Do you want to deposit or withdraw amount?");
            String d = sc.nextLine();
            if ("deposit".equals(d)) {
                Account de = new Account();
                de.deposit();
            }
            else if ("withdraw".equals(d)) {
                Account wi = new Account();
                wi.withdrawl();
                Sav_acct in = new Sav_acct();
                in.interest();
            }
        }
        else if ("Current Account".equals(t)) {
            System.out.println("Do you want to deposit or withdraw amount?");
            String d = sc.nextLine();
            if ("deposit".equals(d)) {
                Account de = new Account();
                de.deposit();
            }
            else if ("withdraw".equals(d)) {
                Account wi = new Account();
                wi.withdrawl();
                if (withdraw < 2000) {
                    Curr_acct pe = new Curr_acct();
                    pe.penalty();
                }
                else {

                }
            }
        }
        else {
            System.out.println("please enter the correct account type as per the options provided on the screen");
        }
    }
}

EDIT : Modified the code.But interest is still 0.

import java.util.Scanner;

class Account {

    String customer_name;
    int account_number;
    String type_account;
    int balance = 2500;
    double deposit;

    double withdraw;

    void deposit() {
        Scanner sc = new Scanner(System.in);
        System.out.println("how much do you want to deposit?");
        int amo = sc.nextInt();
        deposit = balance + amo;

        System.out.println("Your current balance is " + deposit);
    }

    void withdrawl() {

        Scanner sc = new Scanner(System.in);

        System.out.println("how much do you want to withdraw?");

        int amo = sc.nextInt();

        withdraw = balance - amo;

    }

}

class Curr_acct extends Account {

    @SuppressWarnings("empty-statement")

    void penalty() {

        if (withdraw < 2000 && withdraw > 0) {
            double Service_charge = withdraw - 100;
            double falling = Service_charge;
            System.out.println("Your balance is " + withdraw);
            System.out.println("You've been charged a service charge" + " 100" + " due to a below the limit balance");
            System.out.println("Your current amount is " + falling);
        } else if (withdraw <= 0) {
            System.out.println("Your balance is insufficient");
        } else {
            System.out.println("Your current balance is " + withdraw);
        }

    }

}

class Sav_acct extends Account {

    void interest() {
        if (withdraw < 0) {
            System.out.println("Your balance is insufficient");
        } else {
            double interests;

            interests = (1 / 100) * withdraw;
            double total_amount = interests + withdraw;
            System.out.println("Your new balance with interest is " + total_amount);
        }

    }

}

public class publish {

    @SuppressWarnings("empty-statement")

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);

        System.out.println("Enter your name");

        String n = sc.nextLine();

        System.out.println("Enter your account type: Savings Account or Current Account");
        String t = sc.nextLine();

        if ("Savings Account".equals(t)) {
            Sav_acct ac = new Sav_acct();
            System.out.println("Do you want to deposit or withdraw amount?");
            String d = sc.nextLine();
            if ("deposit".equals(d)) {

                ac.deposit();
            } else if ("withdraw".equals(d)) {

                ac.withdrawl();

                ac.interest();

            }
        }

        else if ("Current Account".equals(t)) {
            Curr_acct ac = new Curr_acct();
            System.out.println("Do you want to deposit or withdraw amount?");
            String d = sc.nextLine();
            if ("deposit".equals(d)) {

                ac.deposit();
            } else if ("withdraw".equals(d)) {

                ac.withdrawl();

                ac.penalty();

            }
        } else {

            System.out.println("please enter the correct account type as per the options provided on the screen");

        }

    }
}

Answer 1

Don't use public static in a variable just to access it . Use getter setter to access variables of a class. Thats the right way of doing it.

In your case removing public static will do fine; In Account class

public static double withdraw; 

to 

double withdraw;

You are not maintaining any state while creating object for Account and Sav_acct class.You are creating two different objects to do 1 job. You will never get withdraw value of Account in Sav_acct since both are different objects.

You are not maintaining any state while creating objects for the Account and Sav_acct classes. You are creating two different objects here. You will never get the withdraw value of Account in Sav_acct since both are different objects. Plus you are missing the basics of Inheritence in OOPS

Since Sav_acct is extending the Account class it is inheriting all the properties of Account , so there is no need of creating an object of the Account class. Instead, create an object of Sav_acct and use this obj to perform your operations;

Account wi = new Account();
wi.withdrawl();             
Sav_acct in = new Sav_acct();
in.interest();

to

Sav_acct wi = new Sav_acct();
wi.withdrawl();
wi.interest();

You need to know about how Inheritance works in OOPS. Refer here

The main problem

You are declaring objects multiple times whenever you needed.Eg:-

System.out.println("Enter your account type: Savings Account or Current Account");
String t = sc.nextLine();
if ("Savings Account".equals(t)) {
    System.out.println("Do you want to deposit or withdraw amount?");
    String d = sc.nextLine();
    if ("deposit".equals(d)) {
        Account de = new Account();        // creating Account object  
        de.deposit();
    }
    else if ("withdraw".equals(d)) {
        Account wi = new Account();   // creating Account object  again
        wi.withdrawl();
        Sav_acct in = new Sav_acct();
        in.interest();
    }
}

In the above why create Account de = new Account(); separately for both deposit and withdraw just declare one object after getting the account type name and use it to perform respective jobs.

System.out.println("Enter your account type: Savings Account or Current Account");
String t = sc.nextLine();
if ("Savings Account".equals(t)) {

    Sav_acct acc = new Sav_acct(); //creating sav_acct object here and use 
    
    System.out.println("Do you want to deposit or withdraw amount?");
    String d = sc.nextLine();
    if ("deposit".equals(d)) {
        // Account de = new Account(); no need
        acc.deposit();
    }
    else if ("withdraw".equals(d)) {
        //Account wi = new Account(); no need
        acc.withdrawl();
        //Sav_acct in = new Sav_acct(); no need again
        acc.interest();
    }
}

Redesign your code inside main method otherwise, most of the thing is fine