Question

我面临与In Java, remove empty elements from a list of Strings相同的情况。我尝试了几乎所有资源，但我每次都得到同样的错误"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，我尝试了4种方式，但没有一种方法可行。有人有任何想法吗？

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。这解决了我的问题：

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：

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

无法从String的ArrayList中删除空元素

1 个答案: