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BAEL-5563 Reversing a number (#12153) 

* BAEL-5563 Reverse a number initial commit

* BAEL-5563 Final improvements before PR

* BAEL-5563 Reverse a number - Draft improvements

* BAEL-5563 Reverse a number - Recursive method improvements

* BAEL-5563 Reverse a number - Recursive method improvements

* BAEL-5563 Reverse a number - Remove unused imports

Co-authored-by: Timothy Kruger - Lenny <gapptechnology@gmail.com>
Co-authored-by: claud <180181@virtualwindow.co.za>
This commit is contained in:
Timothy Kruger 2022-05-12 13:52:54 +02:00 committed by GitHub
parent 0bbd9bdc64
commit 9727e555ce
2 changed files with 79 additions and 0 deletions
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45
java-numbers-4/src/main/java/com/baeldung/reversenumber/ReverseNumber.java Normal file
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package com.baeldung.reversenumber;
public class ReverseNumber {
public static int reverseNumberWhileLoop(int number) {
int reversedNumber = 0;
int numberToReverse = Math.abs(number);
while (numberToReverse > 0) {
int mod = numberToReverse % 10;
reversedNumber = reversedNumber * 10 + mod;
numberToReverse /= 10;
}
return number < 0 ? reversedNumber * -1 : reversedNumber;
}
public static int reverseNumberForLoop(int number) {
int reversedNumber = 0;
int numberToReverse = Math.abs(number);
for (; numberToReverse > 0; numberToReverse /= 10) {
int mod = numberToReverse % 10;
reversedNumber = reversedNumber * 10 + mod;
}
return number < 0 ? reversedNumber * -1 : reversedNumber;
}
public static int reverseNumberRecWrapper(int number) {
int output = reverseNumberRec(Math.abs(number), 0);
return number < 0 ? output * -1 : output;
}
private static int reverseNumberRec(int numberToReverse, int recursiveReversedNumber) {
if (numberToReverse > 0) {
int mod = numberToReverse % 10;
recursiveReversedNumber = recursiveReversedNumber * 10 + mod;
numberToReverse /= 10;
return reverseNumberRec(numberToReverse, recursiveReversedNumber);
}
return recursiveReversedNumber;
}
}

34
java-numbers-4/src/test/java/com/baeldung/reversenumber/ReverseNumberUnitTest.java Normal file
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package com.baeldung.reversenumber;
import org.assertj.core.api.Assertions;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.*;
class ReverseNumberUnitTest {
private static final int ORIGINAL_NUMBER = 123456789;
private static final int REVERSED_NUMBER = 987654321;
@Test
void whenReverseNumberWhileLoop_thenOriginalEqualToReverse() {
Assertions.assertThat(ReverseNumber.reverseNumberWhileLoop(ORIGINAL_NUMBER)).isEqualTo(REVERSED_NUMBER);
}
@Test
void whenReverseNumberForLoop_thenOriginalEqualToReverse() {
Assertions.assertThat(ReverseNumber.reverseNumberForLoop(ORIGINAL_NUMBER)).isEqualTo(REVERSED_NUMBER);
}
@Test
void whenReverseNumberRec_thenOriginalEqualToReverse() {
Assertions.assertThat(ReverseNumber.reverseNumberRecWrapper(ORIGINAL_NUMBER)).isEqualTo(REVERSED_NUMBER);
}
@Test
void whenReverseNegativeNumber_thenNumberShouldReverse() {
Assertions.assertThat(ReverseNumber.reverseNumberWhileLoop(ORIGINAL_NUMBER * -1)).isEqualTo(REVERSED_NUMBER * -1);
Assertions.assertThat(ReverseNumber.reverseNumberForLoop(ORIGINAL_NUMBER * -1)).isEqualTo(REVERSED_NUMBER * -1);
Assertions.assertThat(ReverseNumber.reverseNumberRecWrapper(ORIGINAL_NUMBER * -1)).isEqualTo(REVERSED_NUMBER * -1);
}
}