Added Portfolio class

src/main/java/Portfolio.java

@@ -0,0 +1,38 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class Portfolio {
+
+    private final List<Share> shares;
+
+    public Portfolio() {
+        this.shares = new ArrayList<>();
+    }
+
+    public boolean addShare(Share share) {
+        return shares.add(share);
+    }
+
+    public boolean removeShare(Share share) {
+        return shares.remove(share);
+    }
+
+    public List<Share> getShares() {
+        return new ArrayList<>(shares);
+    }
+
+    public List<Share> getShares(String symbol) {
+        List<Share> result = new ArrayList<>();
+        for (Share share : shares) {
+            if (share.getStock().getSymbol().equals(symbol)) {
+                result.add(share);
+            }
+        }
+        return result;
+    }
+
+    public boolean contains(Share share) {
+        return shares.contains(share);
+    }
+
+}