Java 从内部类引用的局部变量必须是 final 或有效 final

local variables referenced from an inner class must be final or effectively final

提问by Bails

This program is the final assignment for my class and I'm have issues figuring out why I'm receiving the error "local variables referenced from an inner class must be final or effectively final". The program is running concurrent threads to sort an array of #'s and then find the high and low values of that array. When I created it without the concurrency, I didn't have this error. I'm struggling as to where to finalize the high and low variable.

这个程序是我班级的最终分配，我在弄清楚为什么我收到错误“从内部类引用的局部变量必须是最终的或有效的最终”时遇到了问题。该程序正在运行并发线程以对#'s 数组进行排序，然后找到该数组的高值和低值。当我在没有并发的情况下创建它时，我没有这个错误。我正在努力确定在哪里确定高低变量。

public void HiLo(int[] numbers){

    int high = numbers[0];
    int low = numbers[0];

    Runnable r2 = new Runnable(){
        @Override
        public void run() {
            System.out.println("The highest value is: ");
            for (int index = 1; index < numbers.length; index++){
                if (numbers[index] > high)
                    high = numbers[index];
                System.out.println(high);
                }
            System.out.println();
            System.out.println("The lowest value is: ");
            for (int ind = 1; ind < numbers.length; ind++){
                if (numbers[ind] < low)
                    low = numbers[ind];
                System.out.println(low);
            }
        }
    };
    pool.execute(r2);
}

This is the block of code producing the error. If I make either the int high = numbers[0]; or int low = numbers[0]; final then I get an error that I can't make that value final and the error for the opposite variable disappears.

这是产生错误的代码块。如果我使 int high = numbers[0]; 或 int low = numbers[0]; final 然后我得到一个错误，我无法将该值设为 final，并且相反变量的错误消失。

Here is the rest of the program. Any help is appreciated.

这是程序的其余部分。任何帮助表示赞赏。

package concurrentthread;

import java.util.Arrays;
import java.util.Scanner;
import java.util.concurrent.Executor;
import java.util.concurrent.Executors;


public class ConcurrentThread {

    static Executor pool = Executors.newFixedThreadPool(2);

public static void main(String[] args) {
    int size;

    Scanner keyboard = new Scanner(System.in);

    ConcurrentThread sort = new ConcurrentThread();
    ConcurrentThread hilo = new ConcurrentThread();

    System.out.println("This program will calculate the highest and lowest "
                + "numbers entered by the user \nand also sort them in "
                + "ascending order");
    System.out.println();
    System.out.print("How many numbers would you like in the array? ");
        size = keyboard.nextInt();

    final int[] numbers = new int[size];

    for (int index = 0; index < numbers.length; index++){
        System.out.print("Please enter a number between 1 and 100: ");
        numbers[index] = keyboard.nextInt(); 
    }

    System.out.println();
    sort.Sort(numbers);
    hilo.HiLo(numbers);

    //System.exit(0);
}

public void Sort(int[] numbers){
    int sort = numbers[0];

    Runnable r1 = () -> {
        Arrays.sort(numbers);
        System.out.println("The sorted values are: ");
        for (int index = 0; index < numbers.length; index++)
            System.out.print(numbers[index] + " ");

        System.out.println();
    };
    pool.execute(r1);
}

public void HiLo(int[] numbers){

    final int high = numbers[0];
    int low = numbers[0];

    Runnable r2 = new Runnable(){
        @Override
        public void run() {
            System.out.println("The highest value is: ");
            for (int index = 1; index < numbers.length; index++){
                if (numbers[index] > high)
                    high = numbers[index];
                System.out.println(high);
                }
            System.out.println();
            System.out.println("The lowest value is: ");
            for (int ind = 1; ind < numbers.length; ind++){
                if (numbers[ind] < low)
                    low = numbers[ind];
                System.out.println(low);
            }
        }
    };
    pool.execute(r2);
}

}

}

采纳答案by Andreas

You keep updating both highand lowinside the run()method, making them by definition not effectively final.

您不断更新方法内部high和low内部run()，根据定义使它们不是有效的最终结果。

Since you don't need them outside the run()method anyway, just move the two lines inside.

由于run()无论如何您都不需要在方法之外使用它们，只需将两行移动到内部即可。

public void HiLo(int[] numbers){

    Runnable r2 = new Runnable(){
        @Override
        public void run() {
            int high = numbers[0];
            int low = numbers[0];
            System.out.println("The highest value is: ");