如果值在数组中，如何返回索引？

Question

I don't know how to return index if a value is found in an array and how to return -1 if it isnt found. I've tried this, but it doesn't work. Could someone help me? Thanks in advance!

import java.util.Scanner;

public class NM {
    public static void main(String[] args) {

        int[] arraynm = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10};

        Scanner sc = new Scanner(System.in);

        System.out.print("Enter a number: ");
        int num = sc.nextInt();

        boolean match = false;

        for (int i = 0; i < arraynm.length; i++) {

            if (num == arraynm[i]) {
                match = true;
                return index;
                break;
            }
        }
        if(!match) {
            return -1;
        }
    }

Answer 1

You can have a method like this

 public int indexInArray(final int value, final int[] arr) {
    for (int i = 0; i < arr.length; i++) {
        if (value == arr[i]) {
            return i;
        }
    }
    return -1;
}

or you can use streams

int index = IntStream.range(0, arraynm.length).filter(i -> num == arraynm[i]).findFirst().orElse(-1);

Answer 2

您可以通过这样做返回。

java.util.Arrays.asList(arraynm).indexOf(num);