I wish I had read this comment before. My java code worked with Scanner class but it quite ugly. (Test case 9 was most troublesome for me)

public static int getMaxRemovedItems7(int [] a, int [] b, int x) {

    int total = 0;
    int max = 0;

    ArrayList<Integer> aPrefix = new ArrayList<>(a.length);
    ArrayList<Integer> bPrefix = new ArrayList<>(b.length);

    for(int i=0; i<a.length && total <= x; i++) {
        total += a[i];
        aPrefix.add(total);
    }
    aPrefix.trimToSize();

    total = 0;
    for(int i=0; i<b.length && total <= x; i++) {
        total += b[i];
        bPrefix.add(total);
    }
    bPrefix.trimToSize();

    int i=0;
    while((i+1)<aPrefix.size() && aPrefix.get(i+1) == 0)
        i++;

    int jStart = 0;
    while((jStart+1)<bPrefix.size() && bPrefix.get(jStart+1) == 0)
        jStart++;

    for(; i<aPrefix.size() && aPrefix.get(i)<=x; i++) {
        int j = nearest(bPrefix, jStart, bPrefix.size()-1, x-aPrefix.get(i));
        if((aPrefix.get(i)+bPrefix.get(j)) > x && (i+j+1) > max) {
            max = i+j+1;
        } else if ((aPrefix.get(i)+bPrefix.get(j)) <= x && (i+j+2) > max) {
            max = i+j+2;
        }
    }

    if(max >= aPrefix.size() + bPrefix.size()) {
        return max;
    }

    i=0;
    if((i+1)<bPrefix.size() && bPrefix.get(i+1) == 0)
        i++;

    jStart = 0;
    while((jStart+1)<aPrefix.size() && aPrefix.get(jStart+1) == 0)
        jStart++;

    for(; i<bPrefix.size() && bPrefix.get(i)<=x; i++) {
        int j = nearest(aPrefix, jStart, aPrefix.size()-1, x-bPrefix.get(i));
        if((bPrefix.get(i)+aPrefix.get(j)) > x && (i+j+1) > max) {
            max = i+j+1;
        } else if ((bPrefix.get(i)+aPrefix.get(j)) <= x && (i+j+2) > max) {
            max = i+j+2;
        }
    }

    return max;
}

private static int nearest(List<Integer> arr, int start, int end, int total) {
    if(start<end) {
        if(start == (end-1)) {
            return Math.abs(arr.get(start)-total) <= Math.abs(arr.get(end)-total) ? 
                    start : end ;
        } else {
            int mid = start + (end-start)/2;
            if(arr.get(mid) == total) {
                while(mid+1 < arr.size() && arr.get(mid) == arr.get(mid+1))
                    mid++;
                return mid;
            } else if (arr.get(mid) > total) {
                while(mid-1 >= 0 && arr.get(mid) == arr.get(mid-1))
                    mid--;
                return nearest(arr, start, mid, total);
            } else {
                while(mid+1 < arr.size() && arr.get(mid) == arr.get(mid+1))
                    mid++;
                return nearest(arr, mid, end, total);
            }
        }
    }
    return start;
}