How Do I Find the Index of an Element in a Java Array?

Retrieving an Element's Index in a Java Array

When searching for an array's indexOf method, it's essential to note that this exact method is not present in Java's base syntax. However, there are alternative approaches using the Arrays utility class to retrieve an element's index effectively.

Approach 1: Arrays.asList (Unsorted Non-primitive Arrays)

For unsorted arrays that are not primitive types (int[], double[], etc.), you can convert it into an ArrayList using java.util.Arrays.asList:

java.util.Arrays.asList(theArray).indexOf(o)

This returns the first occurrence of o in the list (converted from the array) or -1 if not found.

Approach 2: Binary Search (Sorted Arrays)

For sorted arrays, you can leverage the binary search algorithm for faster performance:

java.util.Arrays.binarySearch(theArray, o)

This method returns the index of o in the sorted array or a negative value indicating the insertion point where o should be inserted to maintain sorted order.

Note:

If the array contains primitive types and is not sorted, it's recommended to use alternative solutions such as loop-based iterations provided in other answers. Arrays.asList may compile and run but will provide inaccurate results for primitive arrays that are not sorted.

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