The Binary Search Algorithm

This lesson covers implementing the binary search algorithm in Java, so you understand how to search efficiently. It's for anyone searching "Java binary search implementation."

Binary search is an algorithm for efficiently finding a target value in already-sorted data. It's like opening a dictionary somewhere near the middle and narrowing your search range in half from there.

The example computes the midpoint mid from two positions, low and high, comparing it against the target value and updating low or high to narrow the range. Compared to checking one element at a time from the start, this finds the target value dramatically faster the larger the dataset is.

A common early mistake is not realizing binary search requires the array to already be sorted beforehand. It's a precondition that the data you're searching is already sorted, so don't forget to sort it first.

In real projects, there's also a built-in method, Arrays.binarySearch(), that gives you the same logic without implementing it yourself.

📖 Reference code

static int binarySearch(int[] arr, int target) {
    int low = 0, high = arr.length - 1;
    while (low <= high) {
        int mid = (low + high) / 2;
        if (arr[mid] == target) return mid;
        if (arr[mid] < target) low = mid + 1;
        else high = mid - 1;
    }
    return -1;
}

int[] nums = {1, 3, 5, 7, 9, 11};
System.out.println(binarySearch(nums, 7));
System.out.println(binarySearch(nums, 4));

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