Question

我有这个问题编写一个静态方法，它接受一个字符串的ArrayList和一个整数，并且破坏性地更改ArrayList以删除长度小于整数参数的所有字符串。我有这个代码到目前为止，有人可以解释我哪里出错。它编译但它不会从数组列表中删除任何字符串。

import java.util.*;

public class q4
// Shows adding a string after all occurrences of a string
// constructively in an ArrayList
{

   public static void main(String[] args) throws Exception
   {

      Scanner input = new Scanner(System.in);

      System.out.println("Enter some words (all on one line, separated by spaces):");
      String line = input.nextLine();
      String[] words = line.split(" +");
      ArrayList<String> a = new ArrayList<String>();

      for(int i=0; i<words.length; i++)
      {
         a.add(words[i]);
      }

      System.out.println("The words are stored in an ArrayList");
      System.out.println("The ArrayList is "+a);

      System.out.print("\nEnter a number");

      int len = input.nextInt();

      for(int j=0;j<words.length;j++)
      {
         String b =a.get(j);

         if(b.length()<len)
         {

            a.remove(j);

         }

      } 

      System.out.println("The ArrayList is "+a);

   }

}

Answer 1

删除ArrayList的项目时，请务必减少“j”。此外，尽管不常见，但将for-condition设置为j < a.size()。否则，创建一个单独的变量来在循环之前存储大小，然后再减小它。以下代码应该可以使用。

public static void main(String[] args)
{

    Scanner input = new Scanner(System.in);

    System.out.println("Enter some words (all on one line, separated by spaces):");
    String line = input.nextLine();
    String[] words = line.split(" +");
    ArrayList<String> a = new ArrayList<String>();

    for(int i=0; i<words.length; i++)
    {
        a.add(words[i]);
    }

    System.out.println("The words are stored in an ArrayList");
    System.out.println("The ArrayList is "+a);

    System.out.print("\nEnter a number");

    int len = input.nextInt();

    for(int j=0;j<a.size(); j++)
    {
        String b =a.get(j);

        if(b.length()<len)
        {

            a.remove(j);
            j--;
        }

    } 

    System.out.println("The ArrayList is "+a);
}

Answer 2

您从左到右遍历列表并随时删除项目。这会在删除多个项目时出现问题，因为索引不再匹配。

通过遍历从开始到结束的列表，而不是从开始到结束，可以很容易地修复这个问题。

因为现在，如果您删除某个项目，这不会影响以后要删除的项目：

for (int j = words.length - 1; j >= 0; j--)

Answer 3

import java.util.*;

public class q4
// Shows adding a string after all occurrences of a string
// constructively in an ArrayList
{

   public static ArrayList<String> a;
   public static ArrayList<String> presenter;

   public static void main(String[] args) throws Exception
   {

      Scanner input = new Scanner(System.in);

      System.out.println("Enter some words (all on one line, separated by spaces):");
      String line = input.nextLine();
      String[] words = line.split(" +");
      a = new ArrayList<String>();
      presenter = new ArrayList<String>();

      for(int i=0; i<words.length; i++)
      {

         a.add(words[i]);

      }

      System.out.println("The words are stored in an ArrayList");
      System.out.println("The ArrayList is "+a);

      System.out.print("\nEnter a number");

      int len = input.nextInt();

      for(int j=0;j<words.length;j++)
      {

         String b =a.get(j);

         if((b.length()<len))
         {

            //do nothing

         }

         else
         {

            presenter.add(a.get(j));

         }

      } 

      System.out.print("The ArrayList is " + presenter);

   }
}

这是一个替代方案，因为你说其他代码不起作用，我只是将“好”数据转移到另一个arraylist并打印出那个。

ArrayList和字符串

3 个答案: