Java Binary Search — Free Java Tutorial

TL;DR: Learn Java Binary Search in Java with a free, beginner-friendly tutorial, examples and practice for Indian students on Syllab.in.

Java Binary Search in Java

Binary search finds an element in a sorted array in O(log n) time by repeatedly halving the search space. Compare the middle element with the target: if equal, found; if target is smaller, search left half; if larger, search right half.

Precondition: the array MUST be sorted. Binary search on an unsorted array produces incorrect results.

Iterative and recursive implementations both achieve O(log n) time. Iterative uses O(1) space; recursive uses O(log n) stack space.

Java provides Arrays.binarySearch(arr, target) and Collections.binarySearch(list, target) for sorted arrays and lists.

// Iterative binary search
int binarySearch(int[] arr, int target) {
    int left = 0, right = arr.length - 1;
    while (left <= right) {
        int mid = left + (right - left) / 2;  // avoids overflow
        if (arr[mid] == target) return mid;
        if (arr[mid] < target) left = mid + 1;
     

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