Added streams api questions

Author: rampatra

src/me/ramswaroop/dynamicprogramming/FibonacciNumbers.java

@@ -36,6 +36,7 @@ public static int[] getFirstKFibonacciNumbers(int k) {
     }
 
     public static void main(String a[]) {
+        out.println(Arrays.toString(getFirstKFibonacciNumbers(0)));
         out.println(Arrays.toString(getFirstKFibonacciNumbers(10)));
         out.println(Arrays.toString(getFirstKFibonacciNumbers(46)));
     }

src/me/ramswaroop/java8/Streams.java

@@ -0,0 +1,125 @@
+package me.ramswaroop.java8;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static java.util.Comparator.comparing;
+import static java.util.stream.Collectors.toList;
+
+/**
+ * @author ramswaroop
+ * @version 02/02/2017
+ */
+class Trader {
+
+    private final String name;
+    private final String city;
+
+    public Trader(String n, String c) {
+        this.name = n;
+        this.city = c;
+    }
+
+    public String getName() {
+        return this.name;
+    }
+
+    public String getCity() {
+        return this.city;
+    }
+
+    public String toString() {
+        return "Trader:" + this.name + " in " + this.city;
+    }
+}
+
+class Transaction {
+    private final Trader trader;
+    private final int year;
+    private final int value;
+
+    public Transaction(Trader trader, int year, int value) {
+        this.trader = trader;
+        this.year = year;
+        this.value = value;
+    }
+
+    public Trader getTrader() {
+        return this.trader;
+    }
+
+    public int getYear() {
+        return this.year;
+    }
+
+    public int getValue() {
+        return this.value;
+    }
+
+    public String toString() {
+        return "{" + this.trader + ", " +
+                "year: " + this.year + ", " +
+                "value:" + this.value + "}";
+    }
+}
+
+public class Streams {
+
+    static final Trader raoul = new Trader("Raoul", "Cambridge");
+    static final Trader mario = new Trader("Mario", "Milan");
+    static final Trader alan = new Trader("Alan", "Cambridge");
+    static final Trader brian = new Trader("Brian", "Cambridge");
+
+    static final List<Transaction> transactions = Arrays.asList(
+            new Transaction(brian, 2011, 300),
+            new Transaction(raoul, 2012, 1000),
+            new Transaction(raoul, 2011, 400),
+            new Transaction(mario, 2012, 710),
+            new Transaction(mario, 2012, 700),
+            new Transaction(alan, 2012, 950)
+    );
+
+    public static List<Transaction> getTransactionsIn2011SortedByValue() {
+        return transactions.stream()
+                .filter(t -> t.getYear() == 2011)
+                .sorted(comparing(Transaction::getValue))
+                .collect(toList());
+    }
+
+    public static List<String> findUniqueCities() {
+        return transactions.stream()
+                .map(t -> t.getTrader().getCity())
+                .distinct()
+                .collect(toList());
+    }
+
+    public static List<Trader> getAllTradersFromCambridgeAndSortByName() {
+        return transactions.stream()
+                .map(Transaction::getTrader)
+                .filter(traders -> traders.getCity().equals("Cambridge"))
+                .distinct()
+                .sorted(comparing(Trader::getName))
+                .collect(toList());
+    }
+
+    public static List<String> getAllTraderNamesAndSortByName() {
+        return transactions.stream()
+                .map(t -> t.getTrader().getName())
+                .distinct()
+                .sorted()
+                .collect(toList());
+    }
+    
+    public static boolean areAnyTradersFromMilan() {
+        return transactions.stream()
+                .anyMatch(t -> t.getTrader().getCity().equals("Milan"));
+    }
+
+    public static void main(String[] a) {
+        System.out.println(getTransactionsIn2011SortedByValue());
+        System.out.println(findUniqueCities());
+        System.out.println(getAllTradersFromCambridgeAndSortByName());
+        System.out.println(getAllTraderNamesAndSortByName());
+        System.out.println(areAnyTradersFromMilan());
+    }
+}