Refactor ReverseNumber (#4208)

This commit is contained in:
Piotr Idzik
2023-05-31 08:07:55 +02:00
committed by GitHub
parent b6e78a45ac
commit 4bbc4bd69f
2 changed files with 55 additions and 21 deletions

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@ -1,30 +1,31 @@
package com.thealgorithms.maths; package com.thealgorithms.maths;
import java.lang.IllegalStateException; import java.lang.IllegalArgumentException;
import java.util.NoSuchElementException;
import java.util.Scanner;
public class ReverseNumber { /**
* @brief utility class reversing numbers
*/
final public class ReverseNumber {
private ReverseNumber() {
}
public static void main(String[] args) { /**
int number; * @brief reverses the input number
int reverse = 0; * @param number the input number
* @exception IllegalArgumentException number is negative
try (Scanner sc = new Scanner(System.in)) { * @return the number created by reversing the order of digits of the input number
System.out.println("Enter a number:"); */
number = sc.nextInt(); public static int reverseNumber(int number) {
} catch (NoSuchElementException | IllegalStateException e) { if (number < 0) {
System.out.println("ERROR: Invalid input"); throw new IllegalArgumentException("number must be nonnegative.");
return;
} }
while (number != 0) { int result = 0;
int remainder = number % 10; while (number > 0) {
result *= 10;
reverse = reverse * 10 + remainder; result += number % 10;
number = number / 10; number /= 10;
} }
return result;
System.out.println("The reverse of the given number is: " + reverse);
} }
} }

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@ -0,0 +1,33 @@
package com.thealgorithms.maths;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
import java.util.HashMap;
import org.junit.jupiter.api.Test;
public class ReverseNumberTest {
@Test
public void testReverseNumber() {
HashMap<Integer, Integer> testCases = new HashMap<>();
testCases.put(0, 0);
testCases.put(1, 1);
testCases.put(10, 1);
testCases.put(123, 321);
testCases.put(7890, 987);
for (final var tc : testCases.entrySet()) {
assertEquals(ReverseNumber.reverseNumber(tc.getKey()), tc.getValue());
}
}
@Test
public void testReverseNumberThrowsExceptionForNegativeInput() {
assertThrows(
IllegalArgumentException.class,
() -> ReverseNumber.reverseNumber(-1)
);
}
}