Added the code for "Errors and Exceptions in Java". (#13104)

* Added the code for "Errors and Exceptions in Java".

* Added the unit tests.

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/exceptions_vs_errors/CheckedExceptionExcample.java

@@ -0,0 +1,15 @@
+package com.baeldung.exception.exceptions_vs_errors;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.IOException;
+
+public class CheckedExceptionExcample {
+    public static void main(String[] args) {
+        try (FileInputStream fis = new FileInputStream(new File("test.txt"))) {
+            fis.read();
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/exceptions_vs_errors/ErrorExample.java

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+package com.baeldung.exception.exceptions_vs_errors;
+
+public class ErrorExample {
+    
+    public static void main(String[] args) {
+        overflow();
+    }
+
+    public static void overflow() {
+        System.out.println("overflow...");
+        overflow();
+    }
+
+}

core-java-modules/core-java-exceptions-4/src/main/java/com/baeldung/exception/exceptions_vs_errors/RuntimeExceptionExample.java

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+package com.baeldung.exception.exceptions_vs_errors;
+
+public class RuntimeExceptionExample {
+    public static void main(String[] args) {
+        int[] arr = new int[20];
+
+        arr[20] = 20;
+
+        System.out.println(arr[20]);
+    }
+}

core-java-modules/core-java-exceptions-4/src/test/java/com/baeldung/exception/exceptions_vs_errors/ErrorExampleUnitTest.java

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+package com.baeldung.exception.exceptions_vs_errors;
+
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+// Unit test for the ErrorExample class.
+public class ErrorExampleUnitTest {
+    @Test
+    public void whenMainMethodIsRun_thenStackOverflowError() {
+        Assertions.assertThrows(StackOverflowError.class, 
+            () -> ErrorExample.main(null));
+    }
+}

core-java-modules/core-java-exceptions-4/src/test/java/com/baeldung/exception/exceptions_vs_errors/RuntimeExceptionExampleUnitTest.java

@@ -0,0 +1,13 @@
+package com.baeldung.exception.exceptions_vs_errors;
+
+import org.junit.Test;
+import org.junit.jupiter.api.Assertions;
+
+// Unit test for the RuntimeExceptionExample class.
+public class RuntimeExceptionExampleUnitTest {
+    @Test
+    public void whenMainMethodIsRun_thenArrayIndexOutOfBoundsExceptionIsThrown() {
+        Assertions.assertThrows(ArrayIndexOutOfBoundsException.class, 
+            () -> RuntimeExceptionExample.main(null));
+    }
+}