java - 线程（从数组中返回一个元素）

Question

can someone tell me why the thread returns 0 after running this code, and not the max value from the array (the array must be as large as possible), how can I fix it?

import java.util.Arrays;

public class MyThread extends Thread {

    int[] arr = new int[1000000];

    public static int max(int[] numbers) {
        int maxValue = numbers[0];
        for (int i = 1; i < numbers.length; i++) {
            if (numbers[i] > maxValue) {
                maxValue = numbers[i];
            }
        }
        return maxValue;
    }

    public static int min(int[] numbers) {
        int minValue = numbers[0];
        for (int i = 1; i < numbers.length; i++) {
            if (numbers[i] < minValue) {
                minValue = numbers[i];
            }
        }
        return minValue;
    }

    @Override
    public void run() {
        int maxArr = max(Arrays.stream(arr).toArray());
        System.out.println(maxArr);
    }

    public static void main(String[] args) {
        MyThread Thread1 = new MyThread();
        Thread1.start();
    }
}

Answer 1

Your array cells are not initialized, so all value are zero. Write 666 to arr[0] and have a nice day.

Answer 2

Your array

int[] arr = new int[1000000];

is array that filled with zeros , coz the default value of int is 0 .

You should assign some values to array elements otherwise default values 0 are used.

Answer 3

You are passing an array arr which has only zero for all the index which means you need to initialise the array with values like below.

import java.util.Arrays;

class MyThread extends Thread {

int[] arr = new int[1000000];

public static int max(int[] numbers) {
    int maxValue = numbers[0];
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] > maxValue) {
            maxValue = numbers[i];
        }
    }
    return maxValue;
}

public static int min(int[] numbers) {
    int minValue = numbers[0];
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] < minValue) {
            minValue = numbers[i];
        }
    }
    return minValue;
}

@Override
public void run() {
    //initialise array with values
    for (int i = 0; i < arr.length; i++) {
        arr[i] = i;
    }
    int maxArr = max(Arrays.stream(arr).toArray());
    System.out.println(maxArr);
}

public static void main(String[] args) {
    MyThread Thread1 = new MyThread();
    Thread1.start();
}

}