为什么在$符号之前打印负号？

Question

I am supposed to add a toString method to the banckAccount class.

It should return a name separated by a comma and a space. Ex: "Yana" and balance of 3.03 , the call yana.toString() should return the string "Yana, $3.03" .

I tried to add:

public String toString() {
    return  name + ", " + "$"+ balance;
}

It works when I type in:

"user, $90.01" 

But when I enter

"Bankrupt Government, -$765432.10"

I keep getting:

 "Bankrupt Government, $-765432.1"      

Code:

import java.util.*;

public class BankAccount {

     String name;
     double balance;

     public void deposit (double amount ){
          balance = balance + amount;


     }

     public void withdraw ( double amount) {
          balance = balance - amount ;          
     }

  }//end of class

Answer 1

Your balance is negative so it prints as listed. It needs to be

if(balance < 0){
   balance = balance * -1;
   return  name + ", " + "-$"+ balance;
}
else{
  return  name + ", " + "$"+ balance;
}

Answer 2

Your answer is right here:

return  name + ", " + "$"+ balance;

Java simply concatenates the string as you have defined it. So if balance is a negative number, you will get $ , followed by a negative number.

If you want it to display the - in the proper place, you can do something like this:

String sign = (balance < 0) ? "-" : "";
System.out.println(name + ", " + sign + "$" + Math.abs(balance));

Answer 3

It is quite obvious, what your method toString() is doing. If balance is negative, it is just added to the string with "-" sign after the "$". I would detect, if the balance is positive or not:

private String toString() { if (balance > 0.0) { return name + ", " + "$" + balance; } else { return name + ", -$" + (balance * (-1)); } }

Or

private String toString() { return name + ", " + balance > 0.0 ? ("$" + balance) : ("-$" + (balance * (-1))); }

Answer 4

hope this helps run this program

      import java.util.*;
      import java.io.*;
      public class HelloWorld{
      public String toString() {
        if(balance<0)
        {
            balance= Math.abs(balance);
             return  name + ", " +"-"+ "$"+ balance;
        }else
        {
    return  name + ", " + "$"+ balance;
        }
}
       String name="sachin";
     double balance=-1000.00;
 public void deposit (double amount ){
          balance = balance + amount;


     }
      public void withdraw ( double amount) {
          balance = balance - amount ;          
     }
     public static void main(String []args){
       // System.out.println("Hello World");

            HelloWorld helloWorld = new HelloWorld();

         System.out.println(helloWorld.toString());

     }
}