class 19 default methods in interfaces

Author: MartinFiorde

modules/src/main/java/com/platzi/functional_student_practice/_08_lambda/Syntax.java

@@ -2,6 +2,7 @@
 
 import com.platzi.functional_teacher_theory._06_reference_operator.NombresUtils;
 
+import java.util.Arrays;
 import java.util.List;
 import java.util.function.BiFunction;
 import java.util.function.Predicate;
@@ -10,7 +11,7 @@ public class Syntax {
     public static void main(String[] args) {
 
         System.out.println("////////////////////////////////////////////////////////////////////////////////////");
-        System.out.println("\nCLASS 17\n");
+        System.out.println("\nCLASS 18\n");
 
         // 1 input, no return
         List<String> cursos = NombresUtils.getList("Java", "Functional");

modules/src/main/java/com/platzi/functional_student_practice/_09_defaults/StringFunctions.java

@@ -0,0 +1,49 @@
+package com.platzi.functional_student_practice._09_defaults;
+
+public class StringFunctions {
+    public static void main(String[] args) {
+        System.out.println("////////////////////////////////////////////////////////////////////////////////////");
+        System.out.println("\nCLASS 19\n");
+
+        StringOperation six = () -> 6;
+        // 1b. Execution of default method
+        six.operate("Alumno");
+        // 2b. Execution of concatenated default methods
+        six.reduceAmount(2).operate("Profesor");
+
+        // 3. Execution of .functionSaved() method
+        DoOperation operateFive = text -> System.out.println(text);
+        // 4. Execution of saved function 5 times with "Platzi" String
+        operateFive.execute(5, "Platzi");
+    }
+
+    @FunctionalInterface
+    interface StringOperation {
+        int getAmount();
+
+        // 1. Default method. Functional Interfaces require 1 and only 1 abstract method, but you can add any amount of default methods
+        default void operate(String text) {
+            int x = getAmount();
+            while (x-- > 0) {
+                System.out.println(text);
+            }
+        }
+
+        // 2. Extra default method, wich return another StringOperation Object that can be called operate with a modificed Amount
+        default StringOperation reduceAmount(int x) {
+            int old = getAmount();
+            return () -> old - x;
+        }
+    }
+
+    @FunctionalInterface
+    interface DoOperation {
+        void functionSaved(String text);
+
+        default void execute(int x, String text) {
+            while (x-- > 0) {
+                functionSaved(text);
+            }
+        }
+    }
+}