Checking whether an element exist in an array

Question

A simple Java code for checking whether an element exists in an array or not:

import java.util.Arrays;

public class Main {
    static int[] numbers = {813, 907, 908, 909, 910};

    public static void main(String[] args) {
        int number = 907;
        //Integer number = 907; // the same thing -- it's not found.
        boolean b = Arrays.asList(numbers).contains(number);
        System.out.println(b);  // => false
    }
}

1) Why doesn't it find 907 in the array?

2) If there is a better way of doing it, go ahead and share your knowledge.

UPDATE:

It was said that asList converts your int[] into a List<int[]> with a single member: the original list. However, I expect the following code to give me 1, but it gives me 5:

System.out.println(Arrays.asList(numbers).size());

Answer 1

The problem is that Arrays.asList(numbers) isn't doing what you think. It is converting your int[] into a List<int[]> with a single member: the original list.

You can do a simple linear search or, if your numbers array is always sorted, use Arrays.binarySearch(numbers, 907); and test whether the result is negative (meaning not found).

Answer 2

Lists don't contain primitives, so Arrays.asList(int[]) will produce a List with one entry of type int[].

This code works:

static Integer[] numbers = {813, 907, 908, 909, 910};

public static void main(String[] args) {
    Integer number = 907;
    boolean b = Arrays.asList(numbers).contains(number);
    System.out.println(b);  // => false
}

For your question as what will Arrays.asList(numbers) contain as long as it is an int[]:

This code:

static int[] numbers = {813, 907, 908, 909, 910};

public static void main(String[] args) {
    int number = 907;
    List<int[]> list = Arrays.asList(numbers);

    boolean b = list.contains(number);
    System.out.println(b);  // => false
    System.out.println("list: " + list);
    for(int[] next : list) {
        System.out.println("content: " + Arrays.toString(next));
    }
}

has this result:

false
list: [[I@da89a7]
content: [813, 907, 908, 909, 910]

As you can see, the list contains one element of type int[] (the [[I indicate the int[]). It has the elements that were initially created.