add Function demo examples

fishercoder1534 · fishercoder1534 · commit a768af27830e · 2023-08-20T21:37:35.000-07:00
diff --git a/src/main/java/java8tutorials/functionalInterfaces/FunctionDemo.java b/src/main/java/java8tutorials/functionalInterfaces/FunctionDemo.java
@@ -0,0 +1,61 @@
+package java8tutorials.functionalInterfaces;
+
+import java.util.concurrent.ExecutionException;
+import java.util.function.Function;
+
+public class FunctionDemo {
+
+    public static void main(String... args) throws ExecutionException, InterruptedException {
+        System.out.println("Program started.");
+        FunctionDemo main = new FunctionDemo();
+        String originalInput = "originalInput";
+        String result = main.doWorkInMultipleStepsInSequence(originalInput);
+        System.out.println("Program ended, result: " + result);
+    }
+
+    String doWorkInMultipleStepsInSequence(String messageOne) throws InterruptedException {
+        return doWorkStepTwoAsync(messageOne, doWorkStepTwoFunction);
+    }
+
+    String doWorkStepTwoAsync(String message, Function<String, String> doWorkStepTwoFunction) throws InterruptedException {
+        Thread.sleep(1000);
+        StringBuilder sb = new StringBuilder(message);
+        System.out.println("Spent 1 second doing work in Step Two Async function.");
+        sb.append(",aboutToCallDoWorkStepTwoFunction");
+        String intermediateResult = doWorkStepTwoFunction.apply(sb.toString());
+        return doWorkStepThreeAsync(intermediateResult, doWorkStepThreeFunction);
+    }
+
+    String doWorkStepThreeAsync(String message, Function<String, String> doWorkStepThreeFunction) throws InterruptedException {
+        Thread.sleep(1000);
+        StringBuilder sb = new StringBuilder(message);
+        System.out.println("Spent 1 second doing work in Step Three Async function.");
+        sb.append(",aboutToCallDoWorkStepThreeFunction");
+        return doWorkStepThreeFunction.apply(sb.toString());
+    }
+
+    Function<String, String> doWorkStepTwoFunction = s -> {
+        StringBuilder sb = new StringBuilder(s);
+        try {
+            Thread.sleep(1000);
+            System.out.println("Spent 1 second doing work in Step Two.");
+            sb.append(",stepTwoDone");
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return sb.toString();
+    };
+
+    Function<String, String> doWorkStepThreeFunction = s -> {
+        StringBuilder sb = new StringBuilder(s);
+        try {
+            Thread.sleep(1000);
+            System.out.println("Spent 1 second doing work in Step Three.");
+            sb.append(",stepThreeDone");
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+        return sb.toString();
+    };
+
+}
