ArrayList:[1, 2, 3, 4, 6, 7, 8, 9]
key:3

Output:

true

Case 1: Use Binary Search Because the list is sorted in order and Binary Search has less average time complexity as compared to Linear Search i.e O(logn).

// Java Program to Search ArrayList Element
// Using Binary Search

// Importing generic java libraries
import java.io.*;
import java.util.*;

class GFG {

	// Method to search elements in ArrayList
	static boolean search(int key, ArrayList A)
	{
		// low pointer
		int low = 0;

		// high pointer
		int high = A.size() - 1;

		while (low <= high) {

			// find the mid pointer
			int mid = low + (high - low) / 2;
			if (A.get(mid) == key) {
				return true;
			}
			else if (A.get(mid) < key) {

				// shift the low pointer
				low = mid + 1;
			}
			else {

				// shift the high pointer
				high = mid - 1;
			}
		}
		return false;
	}

	// Main driver method
	public static void main(String[] args)
	{

		// Creating an ArrayList
		ArrayList A = new ArrayList<>();

		// Adding items in the list
		A.add(1);
		A.add(2);
		A.add(3);
		A.add(4);
		A.add(6);
		A.add(7);
		A.add(8);
		A.add(9);

		// Random element to be searched
		int key = 19;

		// Binary search
		boolean check = search(key, A);

		System.out.println(check);

		int key1 = 2;

		// Binary search
		boolean check1 = search(key1, A);

		System.out.println(check1);
	}
}

Output:

false
true

Case 2: 

Input:

List: [2, 3, 3, 4, 4, 5, 6, 7]
key: 2
key: 4

Output:
-1
2

Example: Modify the Binary Search according to the condition

// Java Program to Search ArrayList Element
// Using Binary Search

// Importing generic java libraries
import java.io.*;
import java.util.*;

class GFG {

	// Method to search elements in arrayList
	static int search(int key, ArrayList A)
	{
		// Low pointer
		int low = 0;

		// High pointer
		int high = A.size() - 1;
		int index = -1;
		while (low <= high) {

			// Mid pointer
			int mid = low + (high - low) / 2;
			if (A.get(mid) == key) {

				// Shift the High Pointer
				high = mid - 1;
			}
			else if (A.get(mid) < key) {

				// Storing the index of mid index value
				index = mid;

				// Shift the Low Pointer
				low = mid + 1;
			}

			else {
				high = mid - 1;
			}
		}

		// Return the index
		return index;
	}

	public static void main(String[] args)
	{
		// Creating an ArrayList
		ArrayList A = new ArrayList<>();

		// Adding elements in ArrayList
		A.add(2);
		A.add(3);
		A.add(3);
		A.add(4);
		A.add(4);
		A.add(5);
		A.add(6);
		A.add(7);

		// Key
		int key = 5;

		// Index of smallest greater element
		int index = search(key, A);

		// Print searched element
		System.out.println(index);
	}
}