First draft with of Book.class

Added some simple functions including rent() and calculating
overdueFine()

Book.java

@@ -0,0 +1,61 @@
+class Book
+{
+  private int id;
+  //( AVAILABLE || RENTED || RESERVED || NOT AVAILABLE)
+  private String status;
+  private int[] dueDate = new int[3];
+
+  public Book(int id, String status)
+  {
+    this.id = id;
+    this.status = status;
+  }
+
+  public String getStatus()
+  {
+    return status;
+  }
+
+  public boolean rent(int[] dueDate)
+  {
+    if(status != "AVAILABLE")
+    {
+      return false;
+    }
+
+    this.dueDate = dueDate;
+    status = "RENTED";
+    return true;
+  }
+
+  public void returned()
+  {
+    status = "AVAILABLE";
+  }
+
+  public double overdueFine(int[] currentDay)
+  {
+    double fine;
+    if(currentDay[0] > dueDate[0] || currentDay[1] > (dueDate[1] + 1))
+    {
+      return 5;
+    }
+    else if(currentDay[1] > dueDate[1])
+    {
+      fine = (double)(currentDay[2] + 30 - dueDate[2]) * 0.25;
+    }
+    else
+    {
+      fine = (double)(currentDay[2] - dueDate[2]) * 0.25;
+    }
+
+    if(fine > 5)
+    {
+      return 5;
+    }
+    else
+    {
+      return fine;
+    }
+  }
+}