I've written a program where I want to make the addition and substraction of Strings where all Strings have the length of four and look like "+002", "+569", "-022", "-789" etc. I've tried to do it without using any multiplication, division or remainder, but only with addition and substraction as operations, but my problem is that certain cases don't work yet and I don't see why exactly or how I can fix it because it's difficult with such a long code to see well where the problem is exactly and what I should change. So here is the concerning method:
public static String add(String s1, String s2) {
int number;
int[] s = new int[4];
String result = "";
if (s1.contains("+") && s2.contains("+")) {
result = "+";
for (int i = 1; i < s1.length(); ++i) {
if (!(s1.charAt(i) == 0 || s2.charAt(i) == 0)) {
if ((int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96 < 10) s[i] = (int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96;
else {
s[i] = (s1.charAt(i)) + (int) (s2.charAt(i)) - 106;
++s[i - 1];
}
}
else if (s1.charAt(i) != 0 && s2.charAt(i) != 0) {
s[i] = (int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96;
}
}
}
else if (s1.contains("-") && s1.contains("-")) {
result = "-";
for (int i = 1; i < s1.length(); ++i) {
if ((!(s1.charAt(i) == 0 || s2.charAt(i) == 0))) {
if ((int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96 < 10) s[i] = (int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96;
else {
s[i] = (s1.charAt(i)) + (int) (s2.charAt(i)) - 106;
++s[i - 1];
}
}
else if (s1.charAt(i) != 0 && s2.charAt(i) != 0) {
s[i] = (int) (s1.charAt(i)) + (int) (s2.charAt(i)) - 96;
}
}
}
//if (s1.contains("+") && s1.contains("-") || s1.contains("-") && s1.contains("+"))
else if (s1.contains("+") && s2.contains("-")) {
char[] size1 = new char[s1.length()];
char[] size2 = new char[s1.length()];
for (int i = 1; i < s1.length(); ++i) {
size1[i] = s1.charAt(i);
size2[i] = s2.charAt(i);
}
if (size1[1] > size2[1]) result = "+";
else if (size1[1] == size2[1]) {
if (size1[2] > size2[2]) result = "+";
else if (size1[2] == size2[2]) {
if (size1[3] > size2[3]) result = "+";
else if (size1[3] == size2[3]) return "+000";
else result = "-";
}
else result = "-";
}
else result = "-";
for (int i = 1; i < s1.length(); ++i) {
if (!(s1.charAt(i) == 0 || s2.charAt(i) == 0)) {
if (s1.charAt(1) < s2.charAt(1)) {
if (s1.charAt(2) <= s2.charAt(2)) {
if (s1.charAt(3) > s2.charAt(3)) {
s[2] = 10 - (s2.charAt(2) - s1.charAt(2));
s[3] = 10 - (s1.charAt(3) - s2.charAt(3));
--s[2];
s[1] = (s2.charAt(1) - s1.charAt(1));
}
else {
s[2] = (s2.charAt(2) - s1.charAt(2));
s[3] = (s2.charAt(3) - s1.charAt(3));
s[1] = s2.charAt(1) - s1.charAt(1);
}
}
else {
s[2] = 10 - (s1.charAt(2) - s2.charAt(2));
if (s1.charAt(3) < s2.charAt(3)) s[3] = (s2.charAt(3) - s1.charAt(3));
else {
s[3] = 10 - (s1.charAt(3) - s2.charAt(3));
--s[2];
}
}
}
else if (s1.charAt(i) - s2.charAt(i) < 0 && i == 1) s[i] = s2.charAt(i) - s1.charAt(i);
else if (s1.charAt(i) - s2.charAt(i) < 0 && i > 1) {
s[i] = s2.charAt(i) - s1.charAt(i);
}
else s[i] = s1.charAt(i) - s2.charAt(i);
}
}
}
else {
char[] size1 = new char[s1.length()];
char[] size2 = new char[s1.length()];
for (int i = 1; i < s1.length(); ++i) {
size1[i] = s1.charAt(i);
size2[i] = s2.charAt(i);
}
if (size1[1] < size2[1]) result = "+";
else if (size1[1] == size2[1]) {
if (size1[2] < size2[2]) result = "+";
else if (size1[2] == size2[2]) {
if (size1[3] < size2[3]) result = "+";
else if (size1[3] == size2[3]) return "+000";
else result = "-";
}
else result = "-";
}
else result = "-";
for (int i = 1; i < s1.length(); ++i) {
if (!(s1.charAt(i) == 0 || s2.charAt(i) == 0)) {
if (s1.charAt(1) > s2.charAt(1)) {
if (s1.charAt(2) >= s2.charAt(2)) {
if (s1.charAt(3) < s2.charAt(3)) {
s[2] = 10 - (s1.charAt(2) - s2.charAt(2));
s[3] = 10 - (s2.charAt(3) - s1.charAt(3));
--s[2];
}
else {
s[2] = (s1.charAt(2) - s2.charAt(2));
s[3] = (s1.charAt(3) - s2.charAt(3));
s[1] = s1.charAt(1) - s2.charAt(1);
}
}
}
else if (s1.charAt(i) - s2.charAt(i) > 0 && i == 1) s[i] = s1.charAt(i) - s2.charAt(i);
else if (s1.charAt(i) - s2.charAt(i) > 0 && i > 1) {
s[i] = s1.charAt(i) - s2.charAt(i);
}
else s[i] = s2.charAt(i) - s1.charAt(i);
}
}
}
for (int i = 1; i < s.length; ++i) result += s[i];
return result;
}
Since you are allowed to use charAt(), you can convert the strings on your own:
// String s1 = "+123";
int d1 = (s1.charAt(1) - '0') * 100;
int d2 = (s1.charAt(2) - '0') * 10;
int d3 = (s1.charAt(3) - '0');
int num = d1 + d2 + d3;
Then you can just calculate with this number.