1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2026 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle.checks.coding;
21
22 import java.util.Arrays;
23 import java.util.HashSet;
24 import java.util.Set;
25 import java.util.stream.Collectors;
26
27 import com.puppycrawl.tools.checkstyle.StatelessCheck;
28 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
29 import com.puppycrawl.tools.checkstyle.api.DetailAST;
30 import com.puppycrawl.tools.checkstyle.api.FullIdent;
31 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
32 import com.puppycrawl.tools.checkstyle.utils.CheckUtil;
33
34 /**
35 * <div>
36 * Checks that certain exception types do not appear in a {@code catch} statement.
37 * </div>
38 *
39 * <p>
40 * Rationale: catching {@code java.lang.Exception}, {@code java.lang.Error} or
41 * {@code java.lang.RuntimeException} is almost never acceptable.
42 * Novice developers often simply catch Exception in an attempt to handle
43 * multiple exception classes. This unfortunately leads to code that inadvertently
44 * catches {@code NullPointerException}, {@code OutOfMemoryError}, etc.
45 * </p>
46 *
47 * @since 3.2
48 */
49 @StatelessCheck
50 public final class IllegalCatchCheck extends AbstractCheck {
51
52 /**
53 * A key is pointing to the warning message text in "messages.properties"
54 * file.
55 */
56 public static final String MSG_KEY = "illegal.catch";
57
58 /** Specify exception class names to reject. */
59 private final Set<String> illegalClassNames = Arrays.stream(new String[] {"Exception", "Error",
60 "RuntimeException", "Throwable", "java.lang.Error", "java.lang.Exception",
61 "java.lang.RuntimeException", "java.lang.Throwable", })
62 .collect(Collectors.toCollection(HashSet::new));
63
64 /**
65 * Creates a new {@code IllegalCatchCheck} instance.
66 */
67 public IllegalCatchCheck() {
68 // no code by default
69 }
70
71 /**
72 * Setter to specify exception class names to reject.
73 *
74 * @param classNames
75 * array of illegal exception classes
76 * @since 3.2
77 */
78 public void setIllegalClassNames(final String... classNames) {
79 illegalClassNames.clear();
80 illegalClassNames.addAll(
81 CheckUtil.parseClassNames(classNames));
82 }
83
84 @Override
85 public int[] getDefaultTokens() {
86 return getRequiredTokens();
87 }
88
89 @Override
90 public int[] getRequiredTokens() {
91 return new int[] {TokenTypes.LITERAL_CATCH};
92 }
93
94 @Override
95 public int[] getAcceptableTokens() {
96 return getRequiredTokens();
97 }
98
99 @Override
100 public void visitToken(DetailAST detailAST) {
101 final DetailAST parameterDef =
102 detailAST.findFirstToken(TokenTypes.PARAMETER_DEF);
103 final DetailAST excTypeParent =
104 parameterDef.findFirstToken(TokenTypes.TYPE);
105
106 DetailAST currentNode = excTypeParent.getFirstChild();
107 while (currentNode != null) {
108 final FullIdent ident = FullIdent.createFullIdent(currentNode);
109 final String identText = ident.getText();
110 if (illegalClassNames.contains(identText)) {
111 log(detailAST, MSG_KEY, identText);
112 }
113 currentNode = currentNode.getNextSibling();
114 }
115 }
116
117 }