AgeCalculator changesJava-618 Restore RootCauseFinder code

core-java/src/main/java/com/baeldung/exceptions/RootCauseFinder.java

@@ -0,0 +1,95 @@
+package com.baeldung.exceptions;
+
+import java.time.LocalDate;
+import java.time.Period;
+import java.time.format.DateTimeParseException;
+import java.util.Objects;
+
+/**
+ * Utility class to find root cause exceptions.
+ */
+public class RootCauseFinder {
+
+    public static Throwable findCauseUsingPlainJava(Throwable throwable) {
+        Objects.requireNonNull(throwable);
+        Throwable rootCause = throwable;
+        while (rootCause.getCause() != null) {
+            rootCause = rootCause.getCause();
+        }
+        return rootCause;
+    }
+
+    /**
+     *  Calculates the age of a person from a given date.
+     */
+    static class AgeCalculator {
+
+        private AgeCalculator() {
+        }
+
+        public static int calculateAge(String birthDate) throws CalculationException {
+            if (birthDate == null || birthDate.isEmpty()) {
+                throw new IllegalArgumentException();
+            }
+
+            try {
+                return Period
+                  .between(parseDate(birthDate), LocalDate.now())
+                  .getYears();
+            } catch (DateParseException ex) {
+                throw new CalculationException(ex);
+            }
+        }
+
+        private static LocalDate parseDate(String birthDateAsString) throws DateParseException {
+
+            LocalDate birthDate;
+            try {
+                birthDate = LocalDate.parse(birthDateAsString);
+            } catch (DateTimeParseException ex) {
+                throw new InvalidFormatException(birthDateAsString, ex);
+            }
+
+            if (birthDate.isAfter(LocalDate.now())) {
+                throw new DateOutOfRangeException(birthDateAsString);
+            }
+
+            return birthDate;
+        }
+
+    }
+
+    static class CalculationException extends Exception {
+
+        CalculationException(DateParseException ex) {
+            super(ex);
+        }
+    }
+
+    static class DateParseException extends Exception {
+
+        DateParseException(String input) {
+            super(input);
+        }
+
+        DateParseException(String input, Throwable thr) {
+            super(input, thr);
+        }
+    }
+
+    static class InvalidFormatException extends DateParseException {
+
+        InvalidFormatException(String input, Throwable thr) {
+            super("Invalid date format: " + input, thr);
+        }
+    }
+
+    static class DateOutOfRangeException extends DateParseException {
+
+        DateOutOfRangeException(String date) {
+            super("Date out of range: " + date);
+        }
+
+    }
+
+}

core-java/src/test/java/com/baeldung/exceptions/RootCauseFinderTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.exceptions;
+
+import com.google.common.base.Throwables;
+import org.apache.commons.lang3.exception.ExceptionUtils;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.time.LocalDate;
+import java.time.format.DateTimeParseException;
+import java.time.temporal.ChronoUnit;
+
+import static com.baeldung.exceptions.RootCauseFinder.*;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+/**
+ * Tests the {@link RootCauseFinder}.
+ */
+public class RootCauseFinderTest {
+
+    @Test
+    public void givenBirthDate_whenCalculatingAge_thenAgeReturned() {
+        try {
+            int age = AgeCalculator.calculateAge("1990-01-01");
+            Assertions.assertEquals(1990, LocalDate
+              .now()
+              .minus(age, ChronoUnit.YEARS)
+              .getYear());
+        } catch (CalculationException e) {
+            Assertions.fail(e.getMessage());
+        }
+    }
+
+    @Test
+    public void givenWrongFormatDate_whenFindingRootCauseUsingJava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("010102");
+        } catch (CalculationException ex) {
+            assertTrue(findCauseUsingPlainJava(ex) instanceof DateTimeParseException);
+        }
+    }
+
+    @Test
+    public void givenOutOfRangeDate_whenFindingRootCauseUsingJava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("2020-04-04");
+        } catch (CalculationException ex) {
+            assertTrue(findCauseUsingPlainJava(ex) instanceof DateOutOfRangeException);
+        }
+    }
+
+    @Test
+    public void givenNullDate_whenFindingRootCauseUsingJava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge(null);
+        } catch (Exception ex) {
+            assertTrue(findCauseUsingPlainJava(ex) instanceof IllegalArgumentException);
+        }
+    }
+
+    @Test
+    public void givenWrongFormatDate_whenFindingRootCauseUsingApacheCommons_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("010102");
+        } catch (CalculationException ex) {
+            assertTrue(ExceptionUtils.getRootCause(ex) instanceof DateTimeParseException);
+        }
+    }
+
+    @Test
+    public void givenOutOfRangeDate_whenFindingRootCauseUsingApacheCommons_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("2020-04-04");
+        } catch (CalculationException ex) {
+            assertTrue(ExceptionUtils.getRootCause(ex) instanceof DateOutOfRangeException);
+        }
+    }
+
+    @Test
+    public void givenWrongFormatDate_whenFindingRootCauseUsingGuava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("010102");
+        } catch (CalculationException ex) {
+            assertTrue(Throwables.getRootCause(ex) instanceof DateTimeParseException);
+        }
+    }
+
+    @Test
+    public void givenOutOfRangeDate_whenFindingRootCauseUsingGuava_thenRootCauseFound() {
+        try {
+            AgeCalculator.calculateAge("2020-04-04");
+        } catch (CalculationException ex) {
+            assertTrue(Throwables.getRootCause(ex) instanceof DateOutOfRangeException);
+        }
+    }
+
+}