无法从字符串ArrayList中删除空元素

Question

我面临与In Java, remove empty elements from a list of Strings相同的情况。 我几乎尝试了一切，从资源，我能得到，但每次我得到同样的错误"Exception in thread "main" java.lang.UnsupportedOperationException"

public static void main(String[] args) { 
    String s = "Hello World. Want to code?"; 
    StringTokenizer tokenizer = new StringTokenizer(s, ".!?"); 

    List<String> words = new ArrayList<String>(); 
    List<String> statement = new ArrayList<String>(); 
    List<List<String>> statements = new ArrayList<List<String>>(); 

    // Seperating words by delimiters ".!? 
    while (tokenizer.hasMoreTokens()) { 
     words.add(tokenizer.nextToken()); 
    } 
    // O/p is {{Hello World},{ Want to code}} 

    // seperating words by space. 
    for (int i = 0; i < words.size(); i++) { 
     String[] temp2 = words.get(i).split("\\s+"); 
     statement = Arrays.asList(temp2); 
     statements.add(statement); 
    } 
    // O/P is {{Hello, World},{, Want, to, code}} 

    for (List<String> temp : statements) { 
    // Here i have [, Want, to, code] 

     // Way-1 
     Iterator it = temp.iterator(); 
     String str = (String) it.next(); 
     if(str.isEmpty()) 
      it.remove(); 

     // Way-2 
     temp.removeIf(item -> item.contains("")); 

     // Way-3 
     temp.removeAll(Collections.singleton("")); 

     // Way-4 
     temp.removeAll(Arrays.asList("")); 

     // way-5 
     temp.removeIf(String::isEmpty); 
    } 
} 

正如你所看到的，我已经试过4种方式，他们都不工作。 有人有什么想法吗？

Answer 1

我想我找到了一个解决方案：将List的数据类型更改为ArrayList。这解决了这个问题对我来说：

import java.util.ArrayList; 
import java.util.List; 
import java.util.Arrays; 
import java.util.StringTokenizer; 
import java.util.Collections; 

public class Test { 
    public static void main(String[] args) { 
     String s = "Hello World. Want to code?"; 
     StringTokenizer tokenizer = new StringTokenizer(s, ".!?"); 

     ArrayList<String> words = new ArrayList<String>(); 
     ArrayList<String> statement = new ArrayList<String>(); 
     ArrayList<ArrayList<String>> statements = new ArrayList<ArrayList<String>>(); 

     // Seperating words by delimiters ".!? 
     while (tokenizer.hasMoreTokens()) { 
      words.add(tokenizer.nextToken()); 
     } 
     // O/p is {{Hello World},{ Want to code}} 

     // seperating words by space. 
     for (int i = 0; i < words.size(); i++) { 
      String[] temp2 = words.get(i).split("\\s+"); 
      statement = new ArrayList(); 
      statement.addAll(Arrays.asList(temp2)); 
      statements.add(statement); 
     } 
     // O/P is {{Hello, World},{, Want, to, code}} 

     for (ArrayList<String> temp : statements) { 
     // Here i have [, Want, to, code] 

      // Way-2 
      temp.removeIf(item -> item.equals("")); 
      System.out.println("array: " + temp); 
     } 
    } 
} 

程序的输出是这样的：

array: [Hello, World] 
array: [Want, to, code]