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.whitespace;
21
22 import com.puppycrawl.tools.checkstyle.StatelessCheck;
23 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
24 import com.puppycrawl.tools.checkstyle.api.DetailAST;
25 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
26 import com.puppycrawl.tools.checkstyle.utils.CodePointUtil;
27 import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
28
29 /**
30 * <div>
31 * Checks that there is no whitespace before a token.
32 * More specifically, it checks that it is not preceded with whitespace,
33 * or (if linebreaks are allowed) all characters on the line before are
34 * whitespace. To allow linebreaks before a token, set property
35 * {@code allowLineBreaks} to {@code true}. No check occurs before semicolons in empty
36 * for loop initializers or conditions.
37 * </div>
38 *
39 * @since 3.0
40 */
41 @StatelessCheck
42 public class NoWhitespaceBeforeCheck
43 extends AbstractCheck {
44
45 /**
46 * A key is pointing to the warning message text in "messages.properties"
47 * file.
48 */
49 public static final String MSG_KEY = "ws.preceded";
50
51 /** Control whether whitespace is allowed if the token is at a linebreak. */
52 private boolean allowLineBreaks;
53
54 /**
55 * Creates a new {@code NoWhitespaceBeforeCheck} instance.
56 */
57 public NoWhitespaceBeforeCheck() {
58 // no code by default
59 }
60
61 @Override
62 public int[] getDefaultTokens() {
63 return new int[] {
64 TokenTypes.COMMA,
65 TokenTypes.SEMI,
66 TokenTypes.POST_INC,
67 TokenTypes.POST_DEC,
68 TokenTypes.ELLIPSIS,
69 TokenTypes.LABELED_STAT,
70 };
71 }
72
73 @Override
74 public int[] getAcceptableTokens() {
75 return new int[] {
76 TokenTypes.COMMA,
77 TokenTypes.SEMI,
78 TokenTypes.POST_INC,
79 TokenTypes.POST_DEC,
80 TokenTypes.DOT,
81 TokenTypes.GENERIC_START,
82 TokenTypes.GENERIC_END,
83 TokenTypes.ELLIPSIS,
84 TokenTypes.LABELED_STAT,
85 TokenTypes.METHOD_REF,
86 };
87 }
88
89 @Override
90 public int[] getRequiredTokens() {
91 return CommonUtil.EMPTY_INT_ARRAY;
92 }
93
94 @Override
95 public void visitToken(DetailAST ast) {
96 final int[] line = getLineCodePoints(ast.getLineNo() - 1);
97 final int columnNoBeforeToken = ast.getColumnNo() - 1;
98 final boolean isFirstToken = columnNoBeforeToken == -1;
99
100 if ((isFirstToken || CommonUtil.isCodePointWhitespace(line, columnNoBeforeToken))
101 && !isInEmptyForInitializerOrCondition(ast)) {
102 final boolean isViolation = !allowLineBreaks
103 || !isFirstToken
104 && !CodePointUtil.hasWhitespaceBefore(columnNoBeforeToken, line);
105
106 if (isViolation) {
107 log(ast, MSG_KEY, ast.getText());
108 }
109 }
110 }
111
112 /**
113 * Checks that semicolon is in empty for initializer or condition.
114 *
115 * @param semicolonAst DetailAST of semicolon.
116 * @return true if semicolon is in empty for initializer or condition.
117 */
118 private static boolean isInEmptyForInitializerOrCondition(DetailAST semicolonAst) {
119 boolean result = false;
120 final DetailAST sibling = semicolonAst.getPreviousSibling();
121 if (sibling != null
122 && (sibling.getType() == TokenTypes.FOR_INIT
123 || sibling.getType() == TokenTypes.FOR_CONDITION)
124 && !sibling.hasChildren()) {
125 result = true;
126 }
127 return result;
128 }
129
130 /**
131 * Setter to control whether whitespace is allowed if the token is at a linebreak.
132 *
133 * @param allowLineBreaks whether whitespace should be
134 * flagged at line breaks.
135 * @since 3.0
136 */
137 public void setAllowLineBreaks(boolean allowLineBreaks) {
138 this.allowLineBreaks = allowLineBreaks;
139 }
140
141 }