refactor: DecimalToAnyUsingStack (#5392)

Author: alxkm

src/main/java/com/thealgorithms/stacks/DecimalToAnyUsingStack.java

@@ -6,50 +6,33 @@ public final class DecimalToAnyUsingStack {
     private DecimalToAnyUsingStack() {
     }
 
-    public static void main(String[] args) {
-        assert convert(0, 2).equals("0");
-        assert convert(30, 2).equals("11110");
-        assert convert(30, 8).equals("36");
-        assert convert(30, 10).equals("30");
-        assert convert(30, 16).equals("1E");
-    }
-
     /**
-     * Convert decimal number to another radix
+     * Convert a decimal number to another radix.
      *
      * @param number the number to be converted
      * @param radix the radix
-     * @return another radix
-     * @throws ArithmeticException if <tt>number</tt> or <tt>radius</tt> is
-     * invalid
+     * @return the number represented in the new radix as a String
+     * @throws IllegalArgumentException if <tt>number</tt> is negative or <tt>radix</tt> is not between 2 and 16 inclusive
      */
-    private static String convert(int number, int radix) {
+    public static String convert(int number, int radix) {
+        if (number < 0) {
+            throw new IllegalArgumentException("Number must be non-negative.");
+        }
         if (radix < 2 || radix > 16) {
-            throw new ArithmeticException(String.format("Invalid input -> number:%d,radius:%d", number, radix));
+            throw new IllegalArgumentException(String.format("Invalid radix: %d. Radix must be between 2 and 16.", radix));
+        }
+
+        if (number == 0) {
+            return "0";
         }
-        char[] tables = {
-            '0',
-            '1',
-            '2',
-            '3',
-            '4',
-            '5',
-            '6',
-            '7',
-            '8',
-            '9',
-            'A',
-            'B',
-            'C',
-            'D',
-            'E',
-            'F',
-        };
+
+        char[] tables = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
+
         Stack<Character> bits = new Stack<>();
-        do {
+        while (number > 0) {
             bits.push(tables[number % radix]);
             number = number / radix;
-        } while (number != 0);
+        }
 
         StringBuilder result = new StringBuilder();
         while (!bits.isEmpty()) {

src/test/java/com/thealgorithms/stacks/DecimalToAnyUsingStackTest.java

@@ -0,0 +1,45 @@
+package com.thealgorithms.stacks;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+class DecimalToAnyUsingStackTest {
+
+    @Test
+    void testConvertToBinary() {
+        assertEquals("0", DecimalToAnyUsingStack.convert(0, 2));
+        assertEquals("11110", DecimalToAnyUsingStack.convert(30, 2));
+    }
+
+    @Test
+    void testConvertToOctal() {
+        assertEquals("36", DecimalToAnyUsingStack.convert(30, 8));
+    }
+
+    @Test
+    void testConvertToDecimal() {
+        assertEquals("30", DecimalToAnyUsingStack.convert(30, 10));
+    }
+
+    @Test
+    void testConvertToHexadecimal() {
+        assertEquals("1E", DecimalToAnyUsingStack.convert(30, 16));
+    }
+
+    @Test
+    void testInvalidRadix() {
+        IllegalArgumentException thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(30, 1));
+        assertEquals("Invalid radix: 1. Radix must be between 2 and 16.", thrown.getMessage());
+
+        thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(30, 17));
+        assertEquals("Invalid radix: 17. Radix must be between 2 and 16.", thrown.getMessage());
+    }
+
+    @Test
+    void testNegativeNumber() {
+        IllegalArgumentException thrown = assertThrows(IllegalArgumentException.class, () -> DecimalToAnyUsingStack.convert(-30, 2));
+        assertEquals("Number must be non-negative.", thrown.getMessage());
+    }
+}