BAEL-3146 Source code for article: Checked and Unchecked Exceptions in Java

core-java-modules/core-java-exceptions/src/main/java/com/baeldung/exceptions/CheckedUncheckedExceptions.java

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+package com.baeldung.exceptions;
+
+import java.io.File;
+import java.io.FileInputStream;
+import java.io.FileNotFoundException;
+
+public class CheckedUncheckedExceptions {
+    public static void checkedExceptionWithThrows() throws FileNotFoundException {
+        File file = new File("not_existing_file.txt");
+        FileInputStream stream = new FileInputStream(file);
+    }
+
+    public static void checkedExceptionWithTryCatch() {
+        File file = new File("not_existing_file.txt");
+        try {
+            FileInputStream stream = new FileInputStream(file);
+        } catch (FileNotFoundException e) {
+            e.printStackTrace();
+        }
+    }
+
+    public static int divideByZero() {
+        int numerator = 1;
+        int denominator = 0;
+        return numerator / denominator;
+    }
+
+    public static void checkFile(String fileName) throws IncorrectFileNameException {
+        if (fileName == null || fileName.isEmpty()) {
+            throw new NullOrEmptyException("The filename is null.");
+        }
+        if (!isCorrectFileName(fileName)) {
+            throw new IncorrectFileNameException("Incorrect filename : " + fileName);
+        }
+    }
+
+    private static boolean isCorrectFileName(String fileName) {
+        if (fileName.equals("wrongFileName.txt"))
+            return false;
+        else
+            return true;
+    }
+}

core-java-modules/core-java-exceptions/src/main/java/com/baeldung/exceptions/IncorrectFileNameException.java

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+package com.baeldung.exceptions;
+
+public class IncorrectFileNameException extends Exception {
+    private static final long serialVersionUID = 1L;
+
+    public IncorrectFileNameException(String errorMessage) {
+        super(errorMessage);
+    }
+
+    public IncorrectFileNameException(String errorMessage, Throwable thr) {
+        super(errorMessage, thr);
+    }
+}

core-java-modules/core-java-exceptions/src/main/java/com/baeldung/exceptions/NullOrEmptyException.java

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+package com.baeldung.exceptions;
+
+public class NullOrEmptyException extends RuntimeException {
+
+    private static final long serialVersionUID = 1L;
+
+    public NullOrEmptyException(String errorMessage) {
+        super(errorMessage);
+    }
+
+    public NullOrEmptyException(String errorMessage, Throwable thr) {
+        super(errorMessage, thr);
+    }
+}

core-java-modules/core-java-exceptions/src/test/java/com/baeldung/exceptions/CheckedUncheckedExceptionsUnitTest.java

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+package com.baeldung.exceptions;
+
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import java.io.FileNotFoundException;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Tests the {@link CheckedUncheckedExceptions}.
+ */
+public class CheckedUncheckedExceptionsUnitTest {
+
+    @Test
+    public void whenFileNotExist_thenThrowException() {
+        assertThrows(FileNotFoundException.class, () -> {
+            CheckedUncheckedExceptions.checkedExceptionWithThrows();
+        });
+    }
+
+    public void whenTryCatchExcetpion_thenSuccess() {
+        try {
+            CheckedUncheckedExceptions.checkedExceptionWithTryCatch();
+        } catch (Exception e) {
+            Assertions.fail(e.getMessage());
+        }
+    }
+
+    @Test
+    public void whenDivideByZero_thenThrowException() {
+        assertThrows(ArithmeticException.class, () -> {
+            CheckedUncheckedExceptions.divideByZero();
+        });
+    }
+
+    @Test
+    public void whenInvalidFile_thenThrowException() {
+
+        assertThrows(IncorrectFileNameException.class, () -> {
+            CheckedUncheckedExceptions.checkFile("wrongFileName.txt");
+        });
+    }
+
+    @Test
+    public void whenNullOrEmptyFile_thenThrowException() {
+        assertThrows(NullOrEmptyException.class, () -> {
+            CheckedUncheckedExceptions.checkFile(null);
+        });
+        assertThrows(NullOrEmptyException.class, () -> {
+            CheckedUncheckedExceptions.checkFile("");
+        });
+    }
+}