Add Temperature Conversion Utility (#7066)

- Implements conversions between Celsius, Fahrenheit, and Kelvin
- Includes all 6 conversion methods
- Adds comprehensive unit tests with edge cases
- Fixes #6936

src/main/java/com/thealgorithms/conversions/TemperatureConverter.java

@@ -0,0 +1,46 @@
+package com.thealgorithms.conversions;
+
+/**
+ * A utility class to convert between different temperature units.
+ *
+ * <p>This class supports conversions between the following units:
+ * <ul>
+ *   <li>Celsius</li>
+ *   <li>Fahrenheit</li>
+ *   <li>Kelvin</li>
+ * </ul>
+ *
+ * <p>This class is final and cannot be instantiated.
+ *
+ * @author krishna-medapati (https://github.com/krishna-medapati)
+ * @see <a href="https://en.wikipedia.org/wiki/Conversion_of_scales_of_temperature">Wikipedia: Temperature Conversion</a>
+ */
+public final class TemperatureConverter {
+
+    private TemperatureConverter() {
+    }
+
+    public static double celsiusToFahrenheit(double celsius) {
+        return celsius * 9.0 / 5.0 + 32.0;
+    }
+
+    public static double celsiusToKelvin(double celsius) {
+        return celsius + 273.15;
+    }
+
+    public static double fahrenheitToCelsius(double fahrenheit) {
+        return (fahrenheit - 32.0) * 5.0 / 9.0;
+    }
+
+    public static double fahrenheitToKelvin(double fahrenheit) {
+        return (fahrenheit - 32.0) * 5.0 / 9.0 + 273.15;
+    }
+
+    public static double kelvinToCelsius(double kelvin) {
+        return kelvin - 273.15;
+    }
+
+    public static double kelvinToFahrenheit(double kelvin) {
+        return (kelvin - 273.15) * 9.0 / 5.0 + 32.0;
+    }
+}