Merge Statistics exchange class branch with main

millions/src/main/java/no/ntnu/gruppe53/Exchange.java

@@ -143,13 +143,47 @@ public void advance() {
             }
 
             stock.addNewSalesPrice(changedPrice);
+        }
+    }
 
+    /**
+     * Lists the given amount of stocks sorted by highest increase in sales price since last week.
+     * @param entries amount of stocks to be shown in list
+     * @return a descending list of stocks with the highest price increase since last week
+     * @throws IllegalArgumentException if number of entries in list is negative
+     */
+    public List<Stock> getGainers(int entries) {
+        if (entries < 0) {
+            throw new IllegalArgumentException("Amount of entries in list cannot be negative.");
+        }
 
+        return stockMap.values().stream()
+                .sorted(Comparator.comparing(Stock::getLatestPriceChange).reversed())
+                .filter(stock -> stock.getLatestPriceChange().compareTo(BigDecimal.ZERO) > 0)
+                .limit(entries)
 
+                .collect(Collectors.toList());
+    }
 
+    /**
+     * Lists the given amount of stocks sorted by the stocks with the lowest price increase (or
+     * highest price decrease)
+     * @param entries amount of stocks to be shown in the list
+     * @return a descending list of stocks with the highest price decrease or
+     *         lowest price increase
+     * @throws IllegalArgumentException if number of entries in list is negative
+     */
+    public List<Stock> getLosers(int entries) {
+        if (entries < 0) {
+            throw new IllegalArgumentException("Amount of entries in list cannot be negative.");
         }
 
+        return stockMap.values().stream()
+                .sorted(Comparator.comparing(Stock::getLatestPriceChange))
+                .filter(stock -> stock.getLatestPriceChange().compareTo(BigDecimal.ZERO) < 0)
+                .limit(entries)
 
+                .collect(Collectors.toList());
     }