Implement equals method

src/Customer.java

@@ -5,4 +5,11 @@ public class Customer {
 	Customer(String id) { this.id = id; }
 	
 	String getId() { return id; }
+	
+	@Override
+	public boolean equals(Object o) {
+		Customer c = (Customer) o;
+		
+		return this.id.equals(c.getId());
+	}
 }

src/Stock.java

@@ -5,4 +5,11 @@ public class Stock {
 	Stock(String name) { this.name = name; }
 	
 	String getName() { return name; }
+	
+	@Override
+	public boolean equals(Object o) {
+		Stock s = (Stock) o;
+		
+		return this.name.equals(s.getName());
+	}
 }

src/Trade.java

+/*
+ * This Trade abstract class provides all the methods common 
+ * for both SellTrade and BuyTrade classes that will inherit 
+ * for it.
+ */
 public abstract class Trade {
 	int qty;
 	float price;
@@ -26,4 +31,22 @@ public abstract class Trade {
 	Customer getCustomer() { return c; }
 	
 	Stock getStock() { return stock; }
+
+	@Override
+	public boolean equals(Object o) {
+		// self check
+		if (this == o)	return true;
+		
+		// null check
+		if (o == null) return false;
+		
+		// type check and case
+		if (getClass() != o.getClass()) return false;
+		
+		Trade t = (Trade) o;
+		
+		return this.time == t.getTime() && this.type.equals(t.getType())
+				&& this.c.equals(t.getCustomer()) && this.stock.equals(t.getStock())
+				&& this.qty == t.getQty() && this.price == t.getPrice();
+	}
 }