How to Check if Java Array Contains a Value?

There are many ways to check if Java Array Contains a Value.

• Simple iteration using for loop
• List contains() method
• Stream anyMatch() method
• Arrays.binarySearch() for sorted array

Let’s look into all these methods one at a time.

Using For Loop to check if Java Array Contains a Value

This is the easiest and convenient method to check if the array contains a certain value or not. We will go over the array elements using the for loop and use the equals() method to check if the array element is equal to the given value.

String[] vowels = { "A", "I", "E", "O", "U" };

// using simple iteration over the array elements
for (String s : vowels) {
    if ("E".equals(s)) {
        System.out.println("E found in the vowels list.");
    }
}

Using List to check if Java Array Contains a Value contains() Method

We can use the Arrays class to get the list representation of the array. Then use the contains() method to check if the array contains the value. Let’s use JShell to run the example code snippet.

jshell> String[] vowels = { "A", "I", "E", "O", "U" };
vowels ==> String[5] { "A", "I", "E", "O", "U" }

jshell> List vowelsList = Arrays.asList(vowels);
vowelsList ==> [A, I, E, O, U]

jshell> vowelsList.contains("U")
$3 ==> true

jshell> vowelsList.contains("X")
$4 ==> false

Using Stream anyMatch() Method

If you are using Java 8 or higher, you can create a stream from the array. Then use the anyMatch() method with a lambda expression to check if it contains a given value.

jshell> List vowelsList = Arrays.asList(vowels);
vowelsList ==> [A, I, E, O, U]

jshell> Arrays.stream(vowels).anyMatch("O"::equals);
$5 ==> true

jshell> Arrays.stream(vowels).anyMatch("X"::equals);
$6 ==> false

Arrays.binarySearch() for Sorted Array

If your array is sorted, you can use the Arrays.binarySearch() method to check if the array contains the given value or not.

String[] vowels = { "A", "I", "E", "O", "U" };

System.out.println("Unsorted Array = " + Arrays.toString(vowels));

Arrays.parallelSort(vowels);

System.out.println("Sorted Array = " + Arrays.toString(vowels));

int index = Arrays.binarySearch(vowels, "X");

if (index < 0) {
    System.out.println("X not found in the array");
} else {
    System.out.println("X found in the array");
}

Output:

Unsorted Array = [A, I, E, O, U]
Sorted Array = [A, E, I, O, U]
X not found in the array

Checking if Array Contains Multiple Values

What if we want to check if the array contains multiple values? Let’s say you want to check if a given array is the subset of the source array. We can create nested loops and check each element one by one. There is a cleaner way by converting arrays to lists and then using the containsAll() method.

String[] vowels = { "A", "I", "E", "O", "U" };
String[] subset = { "E", "U" };

boolean foundAll = Arrays.asList(vowels).containsAll(Arrays.asList(subset));

System.out.println("vowels contains all the elements in subset = " + foundAll);

Output:

vowels contains all the elements in subset = true