Arraylist.contains 不会检查字符串

Question

我想构建一个程序，该程序通过扫描仪输入一组字符串 (int T)，并将它们存储在数组列表中。然后我想检查输入以查看它是否匹配或包含来自另一个数组的字符。

示例输入：

1
ABCD

示例输出：

好

问题：当我运行代码时，我没有得到“好”或“坏”的输出，而是出现错误并启动调试控制台。

确切的错误：

Scanner.throwFor() 行：不可用。找不到来源

import java.io.*; 
import java.util.*;

public class RNA {

    public static void main(String[] args) {

        String X [] = {"A", "B", "C", "D"};  // Array to be checked against


        List<String>A = new ArrayList();  // ArrayList to be imported

        Scanner q = new Scanner(System.in);

        System.out.println("How Many Sets of Strings do you want?");

        int T = q.nextInt(); // number of Strings to be imported
        q.nextInt();  // allows to reset Scanner

        for(int i = 0 ; i < T; i ++){

            A.add(q.nextLine());  //imports stuff to add to array A
        }


        Iterator<String> ListChecker = A.iterator(); 

        while((ListChecker.hasNext())) {   //continues as long as DNA Check has an index to go to 

            if (A.contains(X)) {                  //Checks A for X
                System.out.println("Good");       //Prints out good if the check is good
            }
            else {

                System.out.println("Bad");        //Prints out bad if the check is bad
            }
        }

    }

}

Answer 1

切勿对 nextInt() 和 nextLine() 使用相同的扫描仪。他们出故障了。使用两台扫描仪，一台用于整数，一台用于字符串。这将修复您的程序。

Answer 2

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Scanner;

public class RNA {

    public static void main(String[] args) {

        String X [] = {"A", "B", "C", "D"};  // Array to be checked against


        List<String>A = new ArrayList<String>();  // ArrayList to be imported

        Scanner scanner = new Scanner(System.in);

        System.out.println("How Many Sets of Strings do you want?");

        int T = scanner.nextInt(); // number of Strings to be imported

        scanner.nextLine();

        for(int i = 0 ; i < T; i ++) {
            String nextLine = scanner.nextLine();
            A.add(nextLine);  //imports stuff to add to array A
        }

        scanner.close();

        Iterator<String> ListChecker = A.iterator(); 
        while((ListChecker.hasNext())) {   //continues as long as DNA Check has an index to go to 

            if (A.contains(X)) {                  //Checks A for X
                System.out.println("Good");       //Prints out good if the check is good
            }
            else {

                System.out.println("Bad");        //Prints out bad if the check is bad
            }

            ListChecker.next();
        }

    }

}

试试这个。

而不是q.nextInt() 使用q.nextLine() 重置。

Answer 3

你检查 A 是否包含一个字符串数组（直接是 String[] 对象），而不是它是否在这个数组中包含一个字符串（这个 String[] 里面是什么）。

替换为

List<String> result = Arrays.asList(X);

所以你有一个来自数组的列表，然后使用包含

result.contains(A)

您的代码可能如下所示

List<String> xAsList = Arrays.asList(X);

// [....]

while((ListChecker.hasNext())) {   //continues as long as DNA Check has an index to go to
  if (xAsList.contains(ListChecker.next())) { //Checks A for X
    System.out.println("Good");       //Prints out good if the check is good
  } else {
    System.out.println("Bad");//Prints out bad if the check is bad
  }
}

Answer 4

几个问题：

• 您应该使用q.next(); 来使用换行符而不是q.nextInt();，这基本上是您遇到输入不匹配异常。

• 您正在做的list.contains(Array) 不受支持。如果您希望检查用户的每个输入是否在 Array X 中，那么您可能应该执行以下操作：

  List<String> list = Arrays.asList(X);
  while((ListChecker.hasNext())) {   //continues as long as DNA Check has an index to go to 
     if (list.contains(ListChecker.next())) {                  //Checks A for X
         System.out.println("Good");       //Prints out good if the check is good
     } else {
         System.out.println("Bad");        //Prints out bad if the check is bad
     }
  }