Question

我正在尝试编写一个相当简单的程序，它可以计算出一组硬币可以变成更大的硬币（先进入四分之一，剩下的成为硬币，再剩下剩余的硬币）我之前用c ++编写代码我对java的差异有点不清楚。我不确定编译器错误意味着什么，到目前为止搜索已经出现完全不同的情况，使用相同的错误代码。

    public class coins
{
   int input = 0;
   int current_pennies = 0;
   int quarters = 0;
   int dimes = 0;
   int nickels = 0;
   int remainder = 0;



   //input is loaded
    public static void main(String[] args) {
        System.out.println("Please enter the starting number of pennies: ");
   }



import java.util.Scanner;

Scanner in = new Scanner(System.in);
input = in.nextInt();


// current pennies is set to input

current_pennies = input;

//quaters is set equal to  current pennies divided by 25 and floored.

quarters = current_pennies / 25;

//current pennies is set to current pennies, modulo 25. IE the remainder.

current_pennies = current_pennies % 25; 

//dimes is set equal to  current pennies divided by 10 and floored.

dimes = current_pennies / 10;
//current pennies is set to current pennies, modulo 10  IE the remainder.

current_pennies = current_pennies % 10; 
//dimes is set equal to  current pennies divided by 5 and floored.

nickels = current_pennies / 5;

//current pennies is set you current pennies, modulo 5  IE the remainder.

current_pennies = current_pennies % 5; 
//outputting the data

public static void main(String[] args) {
        System.out.println("Number of Quarter s" + quarters);
         System.out.println("Number of Dimes " + dimes);
          System.out.println("Number of Nickels " + nickels);
           System.out.println("Remaining Pennies " + current_pennies);
   }





}

和编译器错误。

 ----jGRASP exec: javac -g coins.java
coins.java:19: error: illegal start of type
import java.util.Scanner;
^
coins.java:19: error: <identifier> expected
import java.util.Scanner;
                        ^
coins.java:22: error: <identifier> expected
input = in.nextInt();
     ^
coins.java:27: error: <identifier> expected
current_pennies = input;
               ^
coins.java:31: error: <identifier> expected
quarters = current_pennies / 25;
        ^
coins.java:35: error: <identifier> expected
current_pennies = current_pennies % 25; 
               ^
coins.java:39: error: <identifier> expected
dimes = current_pennies / 10;
     ^
coins.java:42: error: <identifier> expected
current_pennies = current_pennies % 10; 
               ^
coins.java:45: error: <identifier> expected
nickels = current_pennies / 5;
       ^
coins.java:49: error: <identifier> expected
current_pennies = current_pennies % 5; 
               ^
10 errors

 ----jGRASP wedge2: exit code for process is 1.
 ----jGRASP: operation complete.

Answer 1

所有导入都放在文件的顶部，否则，看起来你的程序实际代码本质上是正确的，我所做的只是删除了类顶部的硬币变量的冗余初始化为0： / p>

import java.util.Scanner;

public class Coins {
  public static void main(String[] args) {
    Scanner scanner = new Scanner(System.in);
    System.out.print("Please enter the starting number of pennies: ");
    // TO DO: Add some form input verfication to ensure program does not crash (InputMismatchException) if user enters a alphabet letter etc. 
    int input = scanner.nextInt();

    // int variable currentPennies is set to input
    int currentPennies = input;

    // int variable quarters is set equal to currentPennies divided by 25 and floored.
    int quarters = (int) Math.floor(currentPennies / 25);

    // currentPennies is set to currentPennies modulo 25, i.e. the remainder.
    currentPennies = currentPennies % 25; 

    // int variable dimes is set equal to currentPennies divided by 10 and floored.
    int dimes =  (int) Math.floor(currentPennies / 10);

    // currentPennies is set to currentPennies modulo 10, i.e the remainder.
    currentPennies = currentPennies % 10; 

    // int variable nickels is set equal to currentPennies divided by 5 and floored.
    int nickels = (int) Math.floor(currentPennies / 5);

    // currentPennies is set to currentPennies modulo 5, i.e the remainder.
    currentPennies = currentPennies % 5; 

    // Outputting the number of each type of coins
    System.out.println("Number of Quarters: " + quarters);
    System.out.println("Number of Dimes: " + dimes);
    System.out.println("Number of Nickels: " + nickels);
    System.out.println("Remaining Pennies: " + currentPennies);
  }
}

使用示例：

Please enter the starting number of pennies:  98
Number of Quarters: 3
Number of Dimes: 2
Number of Nickels: 0
Remaining Pennies: 3

尝试 here 。

您可能会感到困惑的另一件事是某些行上的(int)基本上这是因为Math.floor()方法返回double数据类型，如果我们使用它将意味着我们会得到在输出中没有意义的小数点，或者我们需要专门格式化我们的输出，以便不显示那些小数点（比仅仅转换为int更多的工作）。

如果您想挑战自己，可以尝试实施以下几个扩展程序：

如果用户输入 a 以获得便士的数量，则程序不会崩溃。
使程序不再打印任何您不会收到的硬币，即不打印示例中的Number of Nickels: 0行。

Answer 2

你必须将你的导入放在你的课程之上，如下所示。这是java结构。首先导入，然后编写您打算使用导入库的类。

import java.util.Scanner;

public class coins
{
   int input = 0;
   int current_pennies = 0;
   int quarters = 0;
   int dimes = 0;
   int nickels = 0;
   int remainder = 0;
}

Answer 3

在java中我们使用方法，在方法中编写所有代码是一种很好的做法。此外，所有导入都在一开始就进行，以便编译器在开始编译代码之前包含它们。同样，当你从Java开始时，如果从一开始就遵循正确的命名概念，那就更好了（类名必须始终以大写字母开头）。如果您了解c ++，那么迁移到java会很容易。快乐的编码！

java新手，不清楚语法/编译器错误

3 个答案: