added functional programming demos

.vscode/launch.json

@@ -4,6 +4,20 @@
   // Weitere Informationen finden Sie unter https://go.microsoft.com/fwlink/?linkid=830387
   "version": "0.2.0",
   "configurations": [
+    {
+      "type": "java",
+      "name": "TaschenrechnerInt4",
+      "request": "launch",
+      "mainClass": "TaschenrechnerInt4",
+      "projectName": "PR2-L_ada963eb"
+    },
+    {
+      "type": "java",
+      "name": "TaschenrechnerInt3",
+      "request": "launch",
+      "mainClass": "TaschenrechnerInt3",
+      "projectName": "PR2-L_ada963eb"
+    },
     {
       "type": "java",
       "name": "Teilnehmer4",

FreundesListe/.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "java.project.sourcePaths": ["src"],
+    "java.project.outputPath": "bin",
+    "java.project.referencedLibraries": [
+        "lib/**/*.jar"
+    ]
+}

FreundesListe/README.md

@@ -0,0 +1,18 @@
+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+- `src`: the folder to maintain sources
+- `lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

FreundesListe/src/Freund.java

@@ -0,0 +1,13 @@
+public class Freund {
+  int alter;
+
+  public Freund(int alter) {
+    this.alter = alter;
+  }
+
+  public int altersUnterschied(
+  Freund einFreund)
+  {
+    return alter - einFreund.alter;
+  }
+}

FreundesListe/src/FreundesListe.java

@@ -0,0 +1,43 @@
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Comparator;
+import java.util.List;
+import java.util.stream.Collector;
+import java.util.stream.Collectors;
+
+public class FreundesListe {
+  public static void main(String[] args) throws Exception {
+    ArrayList<Freund> eineListe = new ArrayList<>();
+
+    eineListe.add(new Freund(45));
+    eineListe.add(new Freund(35));
+    eineListe.add(new Freund(67));
+
+/* Alternativen:
+    List<Freund> aufsteigendesAlter = eineListe
+        .stream()
+        .sorted((freund1, freund2) -> freund1.altersUnterschied(freund2))
+        .collect(Collectors.toList());
+
+    List<Freund> aufsteigendesAlter = eineListe
+        .stream()
+        .sorted(Freund::altersUnterschied)
+        .collect(Collectors.toList());
+*/
+
+Comparator<Freund> aufsteigendAlter = (freund1, freund2) ->
+  freund1.altersUnterschied(freund2);
+Comparator<Freund> absteigendAlter =
+  aufsteigendAlter.reversed();
+        
+  List<Freund> aufsteigendesAlter = eineListe
+  .stream().sorted(absteigendAlter)
+  .collect(Collectors.toList());
+
+  ArrayList<Freund> t = new ArrayList<>(aufsteigendesAlter);
+
+
+    for(Freund f : aufsteigendesAlter)
+      System.out.println(f.alter);
+  }
+}

TaschenrechnerInt3/.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "java.project.sourcePaths": ["src"],
+    "java.project.outputPath": "bin",
+    "java.project.referencedLibraries": [
+        "lib/**/*.jar"
+    ]
+}

TaschenrechnerInt3/README.md

@@ -0,0 +1,18 @@
+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+- `src`: the folder to maintain sources
+- `lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

TaschenrechnerInt3/src/MathInteger.java

@@ -0,0 +1,15 @@
+@FunctionalInterface
+interface MathInteger
+{
+  int berechne(int a, int b);
+  
+  default long berechneLong(int a, int b)
+  {
+    return (long)a * (long) b;
+  }
+  
+  static double berechneStatisch(int a, int b)
+  {
+    return (double)a / (double) b;
+  }
+}

TaschenrechnerInt3/src/TaschenrechnerInt3.java

@@ -0,0 +1,15 @@
+public class TaschenrechnerInt3 implements MathInteger {
+  public static void main(String args [])
+  {
+    System.out.println(MathInteger.berechneStatisch(10, 20));
+    TaschenrechnerInt3 meinRechner = new TaschenrechnerInt3();
+    long x = meinRechner.berechneLong(100000, 200000);
+    System.out.println(x);
+  }
+
+  @Override
+  public int berechne(int a, int b) {
+    // TODO Auto-generated method stub
+    throw new UnsupportedOperationException("Unimplemented method 'berechne'");
+  }
+}

TaschenrechnerInt4/.vscode/settings.json

@@ -0,0 +1,7 @@
+{
+    "java.project.sourcePaths": ["src"],
+    "java.project.outputPath": "bin",
+    "java.project.referencedLibraries": [
+        "lib/**/*.jar"
+    ]
+}

TaschenrechnerInt4/README.md

@@ -0,0 +1,18 @@
+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+- `src`: the folder to maintain sources
+- `lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

TaschenrechnerInt4/src/TaschenrechnerInt4.java

@@ -0,0 +1,24 @@
+import java.util.function.IntFunction;
+import java.util.function.IntPredicate;
+
+public class TaschenrechnerInt4 {
+  @FunctionalInterface
+  interface MathInteger {
+    int berechne(int a, int b);
+  }
+
+  public static void main(String args[])
+  {
+    MathInteger addiere = (c, d) -> c + d;
+    MathInteger multipliziere = (x, y) -> x * y;
+    
+    System.out.println(addiere.berechne(10, 20));
+    System.out.println(multipliziere.berechne(10, 20));
+    
+    IntFunction<Integer> quadriere = e -> e * e;
+    System.out.println(quadriere.apply(9));
+    
+    IntPredicate geradeZahl = f -> f % 2 == 0 ? true : false;
+    System.out.println(geradeZahl.test(8));
+  }
+}