My solution i think its easy to use and implement not sure if its efficient though.

public static List<Integer> rotLeft(List<Integer> a, int d) {
        // Loop from 0 to Number of rotations
        for(int i = 0; i < d ; i++)
        {
                // Get the value at first index of list to temp variable
                int temp = a.get(0);
                // remove the first element
                a.remove(0);
                // add it back to list by default it goes to the end
                a.add(temp);
        }
        return a;
}

Below is code i have submitted code using Java8

public static List<Integer> rotLeft(List<Integer> a, int d) {
    int length = a.size();
    if (length < 2) {
        return a;
    }        
    Integer[] rotatedArray= new Integer[length];
    for(int i=0;i<length;i++){
        int target_index = (length - d + i);
        if (target_index > length - 1) {
            target_index = i - d;
        }
        rotatedArray[target_index] = a.get(i);
    }
    return Arrays.asList(rotatedArray);
}

If anyone has suggestions on how to improve this, please let me know! I'm doing my best to learn how to become an efficient programmer.

vector<int> rotLeft(vector<int> a, int d) {
    vector<int> a2(a.size());
    for (int i = 0; i < a2.size(); i++, d++) {
        if (d == a2.size()) {
            d = 0;
        }
        a2[i] = a[d];
    }
    return a2;
}

Java code public static List rotLeft(List a, int d) {

    if(d==0)
    return a;

    while(d>0){
        Integer dup= a.get(0);
        a.remove(0);
        a.add(dup);
        d--;
    }

return a;

}