Question

这是一个添加指定代码的驱动程序

（在//注释中描述），以便它执行以下操作：提示用户输入列表数字（整数）用空格分隔后跟数字0;读取列表中的第一个数字; 进入一个循环，当数字不为0时，创建一个NumberOperations对象，添加 NumberOperations对象为一个名为numOpsList的ArrayList，然后读取下一个数字列表（即循环遍历）。从列表中读取值0后，循环终止。现在使用第二个while循环，打印出ArrayList中的每个NumberOperations对象它的“赔率低于”和“2的权力”。

我在第35行收到错误：

no suitable method found for add(int)
         numOpsList.add(input);
                   ^
    method Collection.add(NumberOperations) is not applicable
      (argument mismatch; int cannot be converted to NumberOperations)
    method List.add(NumberOperations) is not applicable
      (argument mismatch; int cannot be converted to NumberOperations)
    method AbstractCollection.add(NumberOperations) is not applicable
      (argument mismatch; int cannot be converted to NumberOperations)
    method AbstractList.add(NumberOperations) is not applicable
      (argument mismatch; int cannot be converted to NumberOperations)
    method ArrayList.add(NumberOperations) is not applicable
      (argument mismatch; int cannot be converted to NumberOperations)"

任何帮助？

import java.util.Scanner;
import java.util.ArrayList;

/**
 * Demonstrates the NumberOperations class.
 */
public class NumberOpsDriver {

   /**
    * Reads a set of positive numbers from the user until the user enters 0.
    * Prints odds under and powers of 2 under for each number.
    *
    * @param args - Standard commandline arguments
    */
   public static void main(String[] args) {

      Scanner in = new Scanner(System.in);

      // declare and instantiate ArrayList with generic type <NumberOperations>
      ArrayList<NumberOperations> numOpsList = new ArrayList<NumberOperations>();

      // prompt user for set of numbers
      System.out.println("Enter a list of positive integers separated "
      + "with a space followed by 0:");

      // get first user input using in.nextInt()
      int input = in.nextInt();
      // add a while loop as described below: 
      // while the input is not equal to 0 
      // add a new NumberOperations object to numOpsList based on user input
      // get the next user input using in.nextInt()

      while (input != 0)
      {
         numOpsList.add(input);
         input = in.nextInt();
      }

      int index = 0;
      while (index < numOpsList.size()) {
         NumberOperations num = numOpsList.get(index);
         System.out.println("For: " + num);
         System.out.println("\tOdds under:\t" + num.oddsUnder());
         System.out.println("\tPowers of 2 under:\t" + num.powersTwoUnder());

         index++;
      }
   }
}

Answer 1

*ppstrId

您正在使用通用ArrayList来存储numOpsList.add(input);的实例列表。你正在做的是尝试添加NumberOperations。

将您的输入转换为NumbersOperations实例并添加它，或者只使用int

此外，您无需强制使用ArrayList<Integer>来标记输入的结尾。如果没有要阅读的内容，0将返回布尔值false

编辑1

Scanner.hasNext()

Answer 2

我让它正常工作，我必须做@ajb所说的。

import java.util.Scanner;
import java.util.ArrayList;

/**
 * Demonstrates the NumberOperations class.
 */
public class NumberOpsDriver {

   /**
    * Reads a set of positive numbers from the user until the user enters 0.
     * Prints odds under and powers of 2 under for each number.
     *
    * @param args - Standard commandline arguments
    */
   public static void main(String[] args) {

      Scanner in = new Scanner(System.in);

      // declare and instantiate ArrayList with generic type <NumberOperations>
      ArrayList<NumberOperations> numOpsList
         = new ArrayList<NumberOperations>();

      // prompt user for set of numbers
      System.out.println("Enter a list of positive integers separated "
                        + "with a space followed by 0:");

      // get first user input using in.nextInt()
      int input = in.nextInt();
      // add a while loop as described below: 
    // while the input is not equal to 0 
         // add a new NumberOperations object to numOpsList based on user input
         // get the next user input using in.nextInt()

      while (input != 0)
      {
         NumberOperations newOp = new NumberOperations(input);
         numOpsList.add(newOp);
         input = in.nextInt();
      }

      int index = 0;
      while (index < numOpsList.size()) {
         NumberOperations num = numOpsList.get(index);
         System.out.println("For: " + num);
         System.out.println("\tOdds under:\t" + num.oddsUnder());
         System.out.println("\tPowers of 2 under:\t" + num.powersTwoUnder());

         index++;
      }
   }
}

NumberOpsDriver.java:35：错误：没有为add（int）找到合适的方法

2 个答案: