September Morn Update

Task/Extend-your-language/Java/extend-your-language-1.java

@@ -0,0 +1,13 @@
+public class If2 {
+
+    public static void if2(boolean firstCondition, boolean secondCondition,
+                           Runnable bothTrue, Runnable firstTrue, Runnable secondTrue, Runnable noneTrue) {
+        if (firstCondition)
+            if (secondCondition)
+                bothTrue.run();
+            else firstTrue.run();
+        else if (secondCondition)
+            secondTrue.run();
+        else noneTrue.run();
+    }
+}

Task/Extend-your-language/Java/extend-your-language-2.java

@@ -0,0 +1,15 @@
+import static If2.if2;
+class Main {
+    private static void print(String s) {
+        System.out.println(s);
+    }
+
+    public static void main(String[] args) {
+        // prints "both true"
+        if2(true, true,
+                () -> print("both true"),
+                () -> print("first true"),
+                () -> print("second true"),
+                () -> print("none true"));
+    }
+}

Task/Extend-your-language/Java/extend-your-language-3.java

@@ -0,0 +1,41 @@
+public class If2 {
+    private final boolean firstCondition;
+    private final boolean secondCondition;
+
+    public If2(boolean firstCondition, boolean secondCondition) {
+        this.firstCondition = firstCondition;
+        this.secondCondition = secondCondition;
+    }
+
+    public static If2 if2(boolean firstCondition, boolean secondCondition) {
+        return new If2(firstCondition, secondCondition);
+    }
+
+    public If2 then(Runnable runnable) {
+        if (firstCondition && secondCondition) {
+            runnable.run();
+        }
+        return this;
+    }
+
+    public If2 elseNone(Runnable runnable) {
+        if (!firstCondition && !secondCondition) {
+            runnable.run();
+        }
+        return this;
+    }
+
+    public If2 elseIfFirst(Runnable runnable) {
+        if (firstCondition && !secondCondition) {
+            runnable.run();
+        }
+        return this;
+    }
+
+    public If2 elseIfSecond(Runnable runnable) {
+        if (!firstCondition && secondCondition) {
+            runnable.run();
+        }
+        return this;
+    }
+}

Task/Extend-your-language/Java/extend-your-language-4.java

@@ -0,0 +1,14 @@
+// prints "both true"
+if2(true, true)
+    .then(() -> print("both true"))
+    .elseIfFirst(() -> print("first true"))
+    .elseIfSecond(() -> print("second true"))
+    .elseNone(() -> print("none true"));
+
+// if we only care about both true and none true...
+// prints "none true"
+if2(false, false)
+    .then(() -> print("both true"))
+    .elseNone(() -> { // a lambda can have a block body
+        print("none true");
+    });