Added Calculator.java with basic operations

Author: RajorshiDas

src/main/java/com/thealgorithms/Calculator.java

@@ -0,0 +1,8 @@
+package com.thealgorithms.misc;
+
+public class Calculator {
+    public int add(int a, int b) { return a + b; }
+    public int subtract(int a, int b) { return a - b; }
+    public int multiply(int a, int b) { return a * b; }
+    public double divide(int a, int b) { return (b != 0) ? (double)a / b : 0; }
+}