The basic idea behind “isIn” is to inspect an array to see if it contains a given string.

So, in this write-up, we will explore different ways of implementing the “isIn” method in Java.

isIn Java Implementation

Typically, we need to create a static method with two parameters: an array and a given string.

The method should return a boolean value denoting whether the passed string is present in the array.

Using Stream API

Let’s see how we can use the Stream API to achieve our objective:

    
        public static boolean isInUsingStreamApi(String[] array, String value) {
            if (array == null || value == null) {
                return false;
            }

            Optional<String> searchedElement = Arrays.stream(array)
                    .filter(element -> element != null && element.equals(value))
                    .findFirst();
            return searchedElement.isPresent();
        }

To keep things simple, we will not repeat the first condition for the remaining implementations.

Using For-each Loop

Next, we will use a for-each loop to iterate through the array. Then, we will check whether each element is equal to the target.

Here’s an example implementation:

    
        public static boolean isInUsingForLoop(String[] array, String value) {
            for (String str : array) {
                if (str != null && str.equals(value)) {
                    return true;
                }
            }
            return false;
        }

As we can see, we used the equals() method to test if the specified string is in the array.

Using Arrays.binarySearch()

Similarly, we can implement the isIn method using Arrays.binarySearch():

    
        public static boolean isInUsingBinarySearch(String[] array, String value) {
            int result = Arrays.binarySearch(array, value);
            return result >= 0;
        }

Please note that binarySearch() searches for the passed value using the binary search algorithm.

Using Arrays.asList

Alternatively, we can use Arrays.asList() to check whether a string is among the elements:

    
        public static boolean isInUsingArrays(String[] array, String value) {
            return Arrays.asList(array)
                    .contains(value);
        }

As shown above, we called contains() which returns true if the searched value exists in the array. Otherwise, false.

Using HashSet

HashSet provides another way to accomplish the same thing:

    
        public static boolean isInUsingHashSet(String[] array, String value) {
            Set<String> setSet = new HashSet<>(Arrays.asList(array));
            return setSet.contains(value);
        }

Conclusion

In this short article, we demonstrated using practical examples how to implement isIn in Java.