feat: disallow generic exception types check

build.gradle.kts

···
 }
 
 group = "com.nayrid"
-version = "1.0.0"
+version = "1.1.0-SNAPSHOT"
 
 dependencies {
     api(libs.jspecify)

src/main/java/com/nayrid/checks/NoGenericExceptionCheck.java

···
+/*
+ * This file is part of checks, licensed under the MIT License.
+ *
+ * Copyright (c) 2026 nayrid
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.nayrid.checks;
+
+import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
+import com.puppycrawl.tools.checkstyle.api.DetailAST;
+import com.puppycrawl.tools.checkstyle.api.TokenTypes;
+import org.jspecify.annotations.Nullable;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.Set;
+
+/**
+ * Forbids throwing generic exception types.
+ *
+ * @since 1.0.0
+ */
+public final class NoGenericExceptionCheck extends AbstractCheck {
+
+    private static final Set<String> DEFAULT_FORBIDDEN = new HashSet<>(Arrays.asList(
+        "Exception",
+        "Throwable",
+        "RuntimeException",
+        "Error"
+    ));
+
+    private static final String MSG_KEY = "genericExceptionForbidden";
+
+    private Set<String> forbidden = DEFAULT_FORBIDDEN;
+
+    /**
+     * Sets the {@code forbidden} exception types.
+     *
+     * @param forbiddenTypes new types
+     * @since 1.0.0
+     */
+    @SuppressWarnings("MethodName")
+    public void setForbidden(final String[] forbiddenTypes) {
+        this.forbidden = new HashSet<>(Arrays.asList(forbiddenTypes));
+    }
+
+    @Override
+    public int[] getDefaultTokens() {
+        return new int[] { TokenTypes.METHOD_DEF };
+    }
+
+    @Override
+    public int[] getAcceptableTokens() {
+        return this.getDefaultTokens();
+    }
+
+    @Override
+    public int[] getRequiredTokens() {
+        return new int[0];
+    }
+
+    @Override
+    public void visitToken(final DetailAST ast) {
+        final DetailAST modifiers = ast.findFirstToken(TokenTypes.MODIFIERS);
+
+        if (!isPublicOrProtected(modifiers)) {
+            return;
+        }
+
+        final DetailAST throwsClause = ast.findFirstToken(TokenTypes.LITERAL_THROWS);
+        if (throwsClause == null) {
+            return;
+        }
+
+        DetailAST child = throwsClause.getFirstChild();
+        while (child != null) {
+            if (child.getType() == TokenTypes.IDENT) {
+                final String exceptionName = child.getText();
+                if (forbidden.contains(exceptionName)) {
+                    log(child, MSG_KEY, exceptionName);
+                }
+            }
+            child = child.getNextSibling();
+        }
+    }
+
+    private boolean isPublicOrProtected(final @Nullable DetailAST modifiers) {
+        return modifiers != null && (modifiers.findFirstToken(TokenTypes.LITERAL_PUBLIC) != null
+            || modifiers.findFirstToken(TokenTypes.LITERAL_PROTECTED) != null);
+    }
+}

src/main/resources/com/nayrid/checks/messages.properties

···
 missingSince=Javadoc must contain a `@since` tag.
+genericExceptionForbidden=Public API must not throw generic exception type: {0}

src/test/java/com/nayrid/checks/NoGenericExceptionCheckTest.java

···
+/*
+ * This file is part of checks, licensed under the MIT License.
+ *
+ * Copyright (c) 2026 nayrid
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+package com.nayrid.checks;
+
+import com.puppycrawl.tools.checkstyle.AbstractModuleTestSupport;
+import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
+import org.junit.jupiter.api.Test;
+
+import static com.puppycrawl.tools.checkstyle.utils.CommonUtil.EMPTY_STRING_ARRAY;
+
+public class NoGenericExceptionCheckTest extends AbstractModuleTestSupport {
+
+    @Override
+    public String getPackageLocation() {
+        return "com/nayrid/checks/nogenericexception";
+    }
+
+    @Test
+    public void testGenericException() throws Exception {
+        final String[] expected = {
+            "5:30: Public API must not throw generic exception type: Exception",
+        };
+
+        verify(
+            createModuleConfig(NoGenericExceptionCheck.class),
+            getPath("HasGenericException.java"),
+            expected
+        );
+    }
+
+    @Test
+    public void testNonGenericException() throws Exception {
+        verify(
+            createModuleConfig(NoGenericExceptionCheck.class),
+            getPath("HasNonGenericException.java"),
+            EMPTY_STRING_ARRAY
+        );
+    }
+
+
+    @Test
+    public void testNonGenericExceptionConfigured() throws Exception {
+        final DefaultConfiguration checkConfig = createModuleConfig(NoGenericExceptionCheck.class);
+
+        checkConfig.addProperty("forbidden", "NullPointerException");
+
+        final String[] expected = {
+            "5:30: Public API must not throw generic exception type: NullPointerException",
+        };
+
+        verify(
+            checkConfig,
+            getPath("HasNonGenericException.java"),
+            expected
+        );
+    }
+}

src/test/resources/com/nayrid/checks/nogenericexception/HasGenericException.java

···
+package com.nayrid.checks.requiresince;
+
+public class HasGenericException {
+
+    public void foo() throws Exception {
+        throw new Exception("foo");
+    }
+
+}

src/test/resources/com/nayrid/checks/nogenericexception/HasNonGenericException.java

···
+package com.nayrid.checks.requiresince;
+
+public class HasNonGenericException {
+
+    public void foo() throws NullPointerException {
+        throw new NullPointerException("foo");
+    }
+
+}