java - 无法使用java多线程计算元音

Question

这就是我想要做的:

CountVowel.java

package lab2;


/**
 *
 * @author Shyam
 */

public class CountVowel implements Runnable {
    String[] input;
    int vowels = 0;
    char ch;

    public CountVowel(String[] args) {
        input=args;
    }

    public void run() {
        try {
        for (int i = 0; i < input.length; i++) {
                String s = input[i];

                for (int j = 0; j < s.length(); j++) {
                    ch = s.charAt(j);

                    if (ch == 'a' || ch == 'A' || ch == 'e' || ch == 'E' || ch == 'i' || ch == 'I' || ch == 'o'
                            || ch == 'O' || ch == 'u' || ch == 'U')
                        vowels++;
                }
            }
            System.out.println("Vowels : " + vowels);

        } catch (Exception e) {
        }
    }

}

元音线程.java

package lab2;


/**
 *
 * @author Shyam
 */

import java.io.IOException;

public class VowelThread  {

    public static void main(String[] args) 
                throws IOException {
        for (String str : args) {
            System.out.println(str);
        }
        Thread t1 = new Thread(new CountVowel(args));
        t1.start();
    }
}

我尝试了如下不同的方法在 cmd 中输入字符串，但是我没有得到想要的结果。

C:\Users\Shyam\Documents\NetBeansProjects\lab2\src>java VowelCounter hello hello see you in
Error: Could not find or load main class VowelCounter


C:\Users\Shyam\Documents\NetBeansProjects\lab2\src>javac -cp . lab2\VowelThread.java hello hello see you in london
error: Class names, 'hello,hello,see,you,in,london', are only accepted if annotation processing is explicitly requested
1 error

非常感谢您的帮助。

Answer 1

你并没有真正做预期的事情，因为你没有为每个提供的参数创建一个新的 Thread，实际上你只为所有参数创建一个 Thread .

要实现它，您可以使用 FutureTask 并让您的类 CountVowel 实现 Callable，如下所示:

public class CountVowel implements Callable<Integer> {
    private final String input;

    public CountVowel(String input) {
        this.input = input;
    }

    public Integer call() {
        int vowels = 0;
        // Iterate over all the characters of the input String
        for (int j = 0; j < input.length(); j++) {
            // Lower case the current character as we need to ignore the case
            char ch = Character.toLowerCase(input.charAt(j));
            // Use a switch statement instead of an if as it is easier to read and faster
            switch (ch) {
                case 'a':
                case 'e':
                case 'o':
                case 'i':
                case 'u':
                    vowels++;
                    break;
            }
        }
        // Returns the sub total
        return vowels;
    }
}

主类将是这样的:

public class VowelThread {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        // Create the list that will contain all the tasks
        List<FutureTask<Integer>> futures = new ArrayList<>();
        for (String str : args) {
            // Create a task for the current String
            FutureTask<Integer> future = new FutureTask<>(new CountVowel(str));
            // Add the task to the list of tasks
            futures.add(future);
            // Provide the task to a new Thread and start it
            new Thread(future).start();
        }
        int total = 0;
        // Iterate over all the tasks
        for (FutureTask<Integer> task : futures) {
            // Wait as long as it is needed to get the result of the current task
            total += task.get();
        }
        // Print the total of vowels found
        System.out.printf("Number of vowels: %d%n", total);
    }
}

关于问题的第二部分，您需要从 src 目录启动您的 javac 命令，否则它无法编译，因为您的类在包 中lab2 这样它应该位于目录 lab2 中，您可以从该目录启动 javac 命令。

因此假设您在 src 中，预期的命令如下:

javac lab2\VowelThread.java 
java lab2.VowelThread Hello Hello see you in Italy in Venice

输出:

Number of vowels: 15