[BAEL-4990] Throwing exceptions in constructor

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/constructors/exception/Animal.java

@@ -0,0 +1,32 @@
+package com.baeldung.constructors.exception;
+
+import java.io.File;
+import java.io.IOException;
+
+public class Animal {
+
+    public Animal() throws InstantiationException {
+        throw new InstantiationException("Cannot be instantiated");
+    }
+
+    public Animal(String id, int age) {
+        if (id == null)
+            throw new NullPointerException("Id cannot be null");
+        if (age < 0)
+            throw new IllegalArgumentException("Age cannot be negative");
+    }
+
+    public Animal(File file) throws SecurityException, IOException {
+        // Avoiding Path traversal attacks
+        if (file.isAbsolute()) {
+            throw new SecurityException("Traversal attack - absolute path not allowed");
+        }
+        // Avoiding directory traversal
+        // a/../..b/
+        if (!file.getCanonicalPath()
+            .equals(file.getAbsolutePath())) {
+            throw new SecurityException("Directory traversal attempt?");
+        }
+    }
+
+}

core-java-modules/core-java-lang-oop-constructors/src/main/java/com/baeldung/constructors/exception/Bird.java

@@ -0,0 +1,13 @@
+package com.baeldung.constructors.exception;
+
+public class Bird extends Animal {
+
+    // Note that we are throwing parent exception
+    public Bird() throws ReflectiveOperationException {
+        super();
+    }
+
+    public Bird(String id, int age) {
+        super(id, age);
+    }
+}

core-java-modules/core-java-lang-oop-constructors/src/test/java/com/baeldung/constructors/exception/AnimalUnitTest.java

@@ -0,0 +1,47 @@
+package com.baeldung.constructors.exception;
+
+import java.io.File;
+
+import org.assertj.core.api.Assertions;
+import org.junit.Test;
+
+public class AnimalUnitTest {
+
+    @Test
+    public void givenNoArgument_thenFails() {
+        Assertions.assertThatThrownBy(() -> {
+            new Animal();
+        })
+            .isInstanceOf(Exception.class);
+    }
+
+    @Test
+    public void givenInvalidArg_thenFails() {
+        Assertions.assertThatThrownBy(() -> {
+            new Animal(null, 30);
+        })
+            .isInstanceOf(NullPointerException.class);
+    }
+
+    @Test(expected = Test.None.class)
+    public void givenValidArg_thenSuccess() {
+        new Animal("1234", 30);
+    }
+
+    @Test
+    public void givenAbsolutePath_thenFails() {
+        Assertions.assertThatThrownBy(() -> {
+            new Animal(new File("temp.txt").getAbsoluteFile());
+        })
+            .isInstanceOf(SecurityException.class);
+    }
+
+    @Test
+    public void givenDirectoryTraversalPath_thenFails() {
+        Assertions.assertThatThrownBy(() -> {
+            new Animal(new File(File.separator + ".." + File.separator + "temp.txt"));
+        })
+            .isInstanceOf(SecurityException.class);
+    }
+
+}