如何修复“不是声明”？

Question

import java.util.*; // needed for Scanner class  
public class PhoneCalls   
{      
  public static void main (String[] args)         
  {        

    Scanner reader = new Scanner(System.in); // needed to read user input   
    System.out.println ("Enter the length of a phone call in minutues (an integer). ");
    int length=reader.nextInt();
    System.out.println ("Do you have a discount plan (answer 1 for yes and 2 for no):");
    int plan=reader.nextInt();
    (double) cost;
    if (length<=3 && plan==2)         
     (double) cost=.2*length; 
     else if (length<=3 && plan==1)
      (double) cost= 0.2*length*0.6;
     else if (length>3 && plan==2)
      (double) cost = (.2*3)+(.08*(length-3));
      else (double) cost = .2*3 + (.08*(length-3)* 0.6);                      
     System.out.println("The cost of your call is $ ");
     System.out.printf("%.2f.", cost);

  } 
}  

This is to find length of a phone call (an integer) in minutes, and print the cost. Error: '(double) cost;' is not a statement. How do I fix this error?

Answer 1

Replace:

(double) cost;

With

double cost;

And get rid of all the (double) s in your code.

(double) is used to cast another data type to a double.

Answer 2

A type name in parentheses such as (double) means to cast another value as that datatype. To declare a variable with that datatype, remove the parentheses.

double cost;

When referring to a variable that's already declared, there is no need to specify the type again. Remove (double) in multiple locations, such as:

if (length<=3 && plan==2)    
{     
   cost=.2*length; 
}