java - 错误：无效的方法声明；调用方法时需要返回类型错误

Question

大家好，我是一名新的计算机科学专业学生，我正在尝试调用一种方法，但我不断收到此错误。这是我的问题区域：

calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

这是整个代码（不会太长）：

import java.util.Scanner;   
public class SpeedingTicket
{

public static void main(String[] args) 
    //Declarations and Instantiations
{
    // Input Data
    Scanner scan = new Scanner(System.in);

    System.out.println("Enter driver's name: ");
    String driverName = scan.nextLine();

    System.out.println("Enter driver's speed: ");
    int speedDriving = scan.nextInt();

    System.out.println("Enter speed limit: ");
    int speedLimit = scan.nextInt();
    scan.nextLine();

    System.out.println("Was driver in school zone? ");
    String schoolZone = scan.nextLine();

}

    // Call calcTicket

    calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

/** Calculates the cost of a speeding ticket given the speed driven, limit, and if in a school zone.

 */ 
public static void calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone)
{
    // Define constants here

    final int INIT_ADDITIVE = 50;
    final int NO_MULTIPLIER = 6;
    final int YES_MULTIPLIER = 12; 
    final int MAX_ADDITIVE = 200;
    final int EX_THRESH = 30; 

    // Calculations

    int amountOver = (speedDriving - speedLimit);

    if (schoolZone.equalsIgnoreCase("yes"))
    {
        if (amountOver > 0)
            { int fine = amountOver * YES_MULTIPLIER + INIT_ADDITIVE;
            System.out.println(driverName +"owes: $" + fine);
            }
        if (amountOver > EX_THRESH)
            { int fine = amountOver * YES_MULTIPLIER + MAX_ADDITIVE;
            System.out.println(driverName +"owes: $" + fine);
            }
        else 
            { int fine = 0;
            System.out.println(driverName +"owes: $" + fine);
            }
    }

    if (schoolZone.equalsIgnoreCase("no"))  
    {

        if (amountOver > 0)
            { int fine = amountOver * NO_MULTIPLIER + INIT_ADDITIVE;
            System.out.println(driverName +"owes: $" + fine);
            }
        if (amountOver > EX_THRESH)
            { int fine = amountOver * NO_MULTIPLIER + MAX_ADDITIVE;
            System.out.println(driverName +"owes: $" + fine);
            }
        else 
            { int fine = 0;
            System.out.println(driverName +"owes: $" + fine);
            }
    }

}
}       

Answer 1

这部分是问题

// Call calcTicket

calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

你不能让代码在这样的课堂上闲逛。把它放到一个方法中——我想你想把它放在 main() 中：

public static void main(String[] args) 
    //Declarations and Instantiations
{
    // Input Data
    Scanner scan = new Scanner(System.in);

    System.out.println("Enter driver's name: ");
    String driverName = scan.nextLine();

    System.out.println("Enter driver's speed: ");
    int speedDriving = scan.nextInt();

    System.out.println("Enter speed limit: ");
    int speedLimit = scan.nextInt();
    scan.nextLine();

    System.out.println("Was driver in school zone? ");
    String schoolZone = scan.nextLine();

//} --this is not good here!

    // Call calcTicket

    calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

   } //put here instead...

Answer 2

您不是在方法（或构造函数）中调用该方法。将回调放在main方法中。

public static void main(String[] args) 
    //Declarations and Instantiations
{
    // Input Data
    Scanner scan = new Scanner(System.in);

    System.out.println("Enter driver's name: ");
    String driverName = scan.nextLine();

    System.out.println("Enter driver's speed: ");
    int speedDriving = scan.nextInt();

    System.out.println("Enter speed limit: ");
    int speedLimit = scan.nextInt();
    scan.nextLine();

    System.out.println("Was driver in school zone? ");
    String schoolZone = scan.nextLine();

 // Call calcTicket

    calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

}

Answer 3

我不确定当您将代码剪切并粘贴到问题中时格式是否被扭曲，但显然您需要将调用calcTicket拉到main. 像这样的东西：

...
System.out.println("Was driver in school zone? ");
String schoolZone = scan.nextLine();

}

// Call calcTicket

calcTicket(String driverName, int speedDriving, int speedLimit, String schoolZone);

像这样：

System.out.println("Was driver in school zone? ");
String schoolZone = scan.nextLine();

// Call calcTicket
calcTicket(driverName, speedDriving, speedLimit, schoolZone);
}

并确保从调用中删除 arg 类型；它们不是必需的。