Add execute around method pattern (#38)

Author: mperor

DesignPatterns/src/main/java/pl/mperor/lab/java/design/pattern/behavioral/eam/Retry.java

@@ -0,0 +1,37 @@
+package pl.mperor.lab.java.design.pattern.behavioral.eam;
+
+import java.util.function.Supplier;
+
+public class Retry {
+
+    private final int retries;
+
+    private Retry(int retries) {
+        this.retries = retries;
+    }
+
+    public <T> T retry(Supplier<T> action) {
+        Exception lastException = null;
+
+        for (int i = 0; i < retries; i++) {
+            try {
+                return action.get();
+            } catch (Exception e) {
+                lastException = e;
+            }
+        }
+
+        throw new NoRetriesRemainException("Failed to execute action after %s attempts".formatted(retries), lastException);
+    }
+
+    public static Retry of(int retries) {
+        return new Retry(retries);
+    }
+
+    public static class NoRetriesRemainException extends RuntimeException {
+        public NoRetriesRemainException(String message, Throwable cause) {
+            super(message, cause);
+        }
+    }
+
+}

DesignPatterns/src/test/java/pl/mperor/lab/java/design/pattern/behavioral/eam/ExecuteAroundMethodTest.java

@@ -0,0 +1,33 @@
+package pl.mperor.lab.java.design.pattern.behavioral.eam;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+import pl.mperor.lab.common.TestUtils;
+
+import java.util.List;
+import java.util.stream.IntStream;
+
+public class ExecuteAroundMethodTest {
+
+    @Test
+    public void shouldAllowToUseExecuteAroundMethod() {
+        var out = TestUtils.setTempSystemOut();
+        executeAround(() -> System.out.println("action"));
+        Assertions.assertLinesMatch(List.of("setup", "action", "tear down"), out.lines());
+        TestUtils.resetSystemOut();
+    }
+
+    private static void executeAround(Runnable action) {
+        System.out.println("setup");
+        action.run();
+        System.out.println("tear down");
+    }
+
+    @Test
+    public void testRetry() {
+        var exception = Assertions.assertThrows(Retry.NoRetriesRemainException.class, () -> Retry.of(3).retry(() -> 1 / 0));
+        Assertions.assertInstanceOf(ArithmeticException.class, exception.getCause());
+        Assertions.assertEquals(10, Retry.of(1).retry(() -> IntStream.rangeClosed(1, 4).sum()));
+    }
+
+}