+

src/flashcards/Main.java

@@ -1,7 +1,102 @@
 package flashcards;
 
+import java.io.*;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Random;
+import java.util.Scanner;
+
 public class Main {
-    public static void main(String[] args) {
-        System.out.print("Hello world!");
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        boolean exit = false;
+        Map<String,String> cardToDefinition = new HashMap<>();
+        Map<String,String> definitionToCard = new HashMap<>();
+        while (!exit)
+        {
+            String card;
+            String def;
+            System.out.println("Input the action (add, remove, import, export, ask, exit):");
+            switch (br.readLine().toLowerCase())
+            {
+                case "add":
+                    System.out.println("The card:");
+                    card = br.readLine();
+                    System.out.println("The definition of the card:");
+                    def = br.readLine();
+                    cardToDefinition.put(card,def);
+                    definitionToCard.put(def,card);
+                    break;
+                case "remove":
+                    System.out.println("The card:");
+                    card = br.readLine();
+                    if (cardToDefinition.containsKey(card)&&definitionToCard.containsValue(card))
+                    {
+                        definitionToCard.remove(cardToDefinition.get(card));
+                        cardToDefinition.remove(card);
+                        System.out.println("Card \""+card+"\" has been removed.");
+                    }
+                    else
+                    {
+                        System.out.println("Can't remove \""+card+"\": there is no such card.");
+                    }
+                    break;
+                case "import":
+                    System.out.println("File name:");
+                    try (FileReader fr = new FileReader(br.readLine()))
+                    {
+                        cardToDefinition.clear();
+                        definitionToCard.clear();
+                        Scanner s = new Scanner(fr);
+                        while (s.hasNextLine())
+                        {
+                            card = s.nextLine();
+                            def = s.nextLine();
+                            cardToDefinition.put(card,def);
+                            definitionToCard.put(def,card);
+                        }
+                    }
+                    catch (Exception ex)
+                    {
+                        System.out.println(ex.getMessage());
+                    }
+                    break;
+                case "export":
+                    System.out.println("File name:");
+                    try (FileWriter fw = new FileWriter(br.readLine(),false))
+                    {
+                        for (Map.Entry<String, String> entry : cardToDefinition.entrySet()) {
+                            fw.write(entry.getKey()+"\n");
+                            fw.write(entry.getValue()+"\n");
+                        }
+                        fw.flush();
+                    }
+                    catch (Exception ex)
+                    {
+                        System.out.println(ex.getMessage());
+                    }
+                    break;
+                case "ask":
+                    System.out.println("How many times to ask?");
+                    int count = Integer.parseInt(br.readLine());
+                    for (int i = 0; i < count; i++) {
+                        Random rnd = new Random();
+                        int n = rnd.nextInt(cardToDefinition.size());
+                        Map.Entry<String, String> cardentry = (Map.Entry<String, String>)cardToDefinition.entrySet().toArray()[n];
+                        System.out.println("Print the definition of \""+cardentry.getKey()+"\":");
+                        String answer = br.readLine();
+                        if (cardentry.getValue().equals(answer)) System.out.println("Correct answer.");
+                        else
+                            System.out.println("Wrong answer (the correct one is \""+cardentry.getValue()+"\""+(definitionToCard.containsKey(answer)?
+                                    ", you've just written a definition of \""+definitionToCard.get(answer) +"\" card).": ")."));
+                    }
+                    break;
+                case "exit":
+                    exit = true;
+                    System.out.println("Bye bye!");
+                    break;
+            }
+            System.out.println();
+        }
     }
 }