twoSum Algorithm : How to improve this?

Question

I felt like doing an algorithm and found this problem on leetcode

Given an array of integers, find two numbers such that they add up to a specific target num

Answer 1

We can do with HashMap and the time complexity would be O(n)

public class ReturnIndicesOfElementsAddToSum {

public static void main(String[] args) {
    int[] nums = {2, 7, 11, 15};
    int target = 18;

    if(!getIndices(nums,target)) {
        System.out.println("No such numbers found");
    }

}

static boolean getIndices(int[] nums, int target) {
    Map indexMap = new HashMap<>();
    boolean numFound = false;
    for(int i=0;i

}