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// SumBigIntegerOctal.java
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import java.math.BigInteger;
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public class SumBigIntegerOctal {
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public static void main(String[] args) {
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BigInteger sum = new BigInteger("0");
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for (String argument : args) {
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StringBuilder number = new StringBuilder();
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for (char c : argument.toCharArray()) {
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if (!Character.isWhitespace(c)) {
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number.append(c);
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} else {
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sum = sum.add(parseNumber(number));
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number = new StringBuilder();
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}
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}
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sum = sum.add(parseNumber(number));
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}
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System.out.println(sum);
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}
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static BigInteger parseNumber(StringBuilder number) {
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if (!number.isEmpty()) {
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String numberString = number.toString();
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int numberStringLength = numberString.length();
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if (numberString.endsWith("o") || numberString.endsWith("O")) {
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return new BigInteger(
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number.substring(0, numberStringLength - 1),
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8
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);
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} else {
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return new BigInteger(numberString);
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}
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} else {
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return BigInteger.ZERO;
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}
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}
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}
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@@ -0,0 +1,228 @@
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---
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title: SumBigIntegerOctal
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weight: 6
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---
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# Task
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- Input data fits into [`BigInteger`](https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html) data type.
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- Octal numbers ends with `o`.
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- Class should be named `SumBigIntegerOctal`.
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## Solution
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Let's change our `parseNumber` method code from `SumLongOctal` modification. Here's what it looked like
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```java
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static long parseNumber(StringBuilder number) {
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if (!number.isEmpty()) {
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String numberString = number.toString();
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int numberStringLength = numberString.length();
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if (numberString.endsWith("o") || numberString.endsWith("O")) {
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return new BigInteger(
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number.substring(0, numberStringLength - 1),
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8
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).longValue();
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} else {
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return Long.parseLong(numberString);
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}
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} else {
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return 0;
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}
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}
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```
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First of all let's change the output type of our method to `BigInteger`.
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```java
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static BigInteger parseNumber(StringBuilder number) {...}
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```
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Also in case of an empty number we can't just `return 0` anymore because it doesn't have `BigInteger` data type. Instead we are going to return [`BigInteger.ZERO`](https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#ZERO).
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Here we can get rid of `.longValue()` because we just need straight `BigInteger` type.
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```java
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return new BigInteger(number.substring(0, numberStringLength - 1), 8); // .longValue();
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```
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Also we change this
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```java
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return Long.parseLong(numberString);
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```
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to this
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```java
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return new BigInteger(numberString);
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```
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for the same reason. So the `parseNumber` will look like this
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```java
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static BigInteger parseNumber(StringBuilder number) {
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if (!number.isEmpty()) {
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String numberString = number.toString();
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int numberStringLength = numberString.length();
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if (numberString.endsWith("o") || numberString.endsWith("O")) {
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return new BigInteger(
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number.substring(0, numberStringLength - 1),
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8
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);
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} else {
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return new BigInteger(numberString);
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}
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} else {
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return BigInteger.ZERO;
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}
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}
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```
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Let's rework our `main` method as well. Here's what it looks like now
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```java
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public static void main(String[] args) {
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int sum = 0;
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for (String argument : args) {
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StringBuilder number = new StringBuilder();
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for (char c : argument.toCharArray()) {
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if (!Character.isWhitespace(c)) {
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number.append(c);
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} else {
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sum += parseNumber(number);
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number = new StringBuilder();
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}
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}
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sum += parseNumber(number);
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}
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System.out.println(sum);
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}
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```
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First of all, let's change the data type of `sum` to `BigInteger` like this
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```java
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BigInteger sum = new BigInteger("0");
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```
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> [!IMPORTANT]
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> Notice, we can't just do `new BigInteger()` (without any arguments) like we did with `StringBuilder`. We need to put the initial value as an argument like [`new BigInteger(String val)`](https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#BigInteger-java.lang.String-).
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So in this stage our code will look like this
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```java
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// SumBigIntegerOctal.java
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import java.math.BigInteger;
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public class SumBigIntegerOctal {
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public static void main(String[] args) {
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BigInteger sum = new BigInteger("0");
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for (String argument : args) {
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StringBuilder number = new StringBuilder();
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for (char c : argument.toCharArray()) {
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if (!Character.isWhitespace(c)) {
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number.append(c);
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} else {
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sum += parseNumber(number);
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number = new StringBuilder();
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}
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}
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sum += parseNumber(number);
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}
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System.out.println(sum);
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}
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static BigInteger parseNumber(StringBuilder number) {
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if (!number.isEmpty()) {
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String numberString = number.toString();
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int numberStringLength = numberString.length();
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if (numberString.endsWith("o") || numberString.endsWith("O")) {
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return new BigInteger(
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number.substring(0, numberStringLength - 1),
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8
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);
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} else {
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return new BigInteger(numberString);
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}
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} else {
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return BigInteger.ZERO;
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}
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}
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}
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```
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And let's try to compile this
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```bash
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$ javac SumBigIntegerOctal.java
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SumBigIntegerOctal.java:15: error: bad operand types for binary operator '+'
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sum += parseNumber(number);
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^
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first type: BigInteger
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second type: BigInteger
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SumBigIntegerOctal.java:20: error: bad operand types for binary operator '+'
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sum += parseNumber(number);
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^
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first type: BigInteger
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second type: BigInteger
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2 errors
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```
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> [!NOTE]
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> We can't use `+` operand with `BigInteger` data type. Instead we need to use [`BigInteger.add(BigInteger val)`](https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html#add-java.math.BigInteger-).
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So we will modify like so
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```java
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// SumBigIntegerOctal.java
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import java.math.BigInteger;
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public class SumBigIntegerOctal {
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public static void main(String[] args) {
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BigInteger sum = new BigInteger("0");
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for (String argument : args) {
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StringBuilder number = new StringBuilder();
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for (char c : argument.toCharArray()) {
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if (!Character.isWhitespace(c)) {
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number.append(c);
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} else {
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sum = sum.add(parseNumber(number));
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number = new StringBuilder();
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}
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}
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sum = sum.add(parseNumber(number));
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}
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System.out.println(sum);
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}
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static BigInteger parseNumber(StringBuilder number) {
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if (!number.isEmpty()) {
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String numberString = number.toString();
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int numberStringLength = numberString.length();
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if (numberString.endsWith("o") || numberString.endsWith("O")) {
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return new BigInteger(
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number.substring(0, numberStringLength - 1),
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8
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);
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} else {
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return new BigInteger(numberString);
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}
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} else {
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return BigInteger.ZERO;
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}
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}
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}
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```
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And this code will pass all the tests!
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