Imagine you're implementing a horizontal RecyclerView and you want the items inside it to have equal space.

MyAdapter.java

// This snippet should be in your adapter class

@Override
public void onBindViewHolder(@NonNull MyViewHolder holder, int position) {

    // Set grid items spacing
    if (holder.container.getLayoutParams() instanceof ViewGroup.MarginLayoutParams) {
        ViewGroup.MarginLayoutParams p = (ViewGroup.MarginLayoutParams) holder.container.getLayoutParams();

        int marginStart = 16; // 16dp
        p.setMarginStart((int) (marginStart * holder.container.getResources().getDisplayMetrics().density));

        // Last position
        if (position == getItemCount()-1) {
            int marginEnd = 16; // 16dp
            p.setMarginEnd((int) (marginEnd * holder.container.getResources().getDisplayMetrics().density));
        }
        // Other position
        else {
            p.setMarginEnd(0); // No margin
        }
        holder.container.requestLayout();
    }

}

static class MyViewHolder extends RecyclerView.ViewHolder {
    View container;

    MyViewHolder(View v) {
        super(v);
        container = v;
    }
}