TwoSum.java

public int[] twoSum(int[] nums, int target) {
        // inserted Value & Indices
        HashMap<Integer, Integer> map = new HashMap<>();
        
        // Filling the HashMap
        for(int i = 0; i < nums.length; i++){
            map.put(nums[i], i);
        }
        
        // Searching for the target indices
        for(int i = 0; i < nums.length; i++){
            // I will get my first element Example:- [2,7,11,15], target = 9
            int num = nums[i]; // I will get 2 
            int rem = target - num; // Calculating remaining value = 9 - 2 = 7 will get from here
            if(map.containsKey(rem)){ // Now I will check is on any index 7 present.
                int index = map.get(rem); // From here i will get the index for no. 7
                if(index == i) continue; // By doing this i will handle the case to not select more then one of yourself.
                return new int[]{i, index}; // returning the array with their indices.
            }
        }
        return new int[]{}; // If we unable to found return empty array.
    }