Coverage Report - com.puppycrawl.tools.checkstyle.checks.coding.OneStatementPerLineCheck
 
Classes in this File Line Coverage Branch Coverage Complexity
OneStatementPerLineCheck
100%
61/61
100%
42/42
3.222
 
 1  
 ////////////////////////////////////////////////////////////////////////////////
 2  
 // checkstyle: Checks Java source code for adherence to a set of rules.
 3  
 // Copyright (C) 2001-2017 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.ArrayDeque;
 23  
 import java.util.Deque;
 24  
 
 25  
 import com.puppycrawl.tools.checkstyle.FileStatefulCheck;
 26  
 import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
 27  
 import com.puppycrawl.tools.checkstyle.api.DetailAST;
 28  
 import com.puppycrawl.tools.checkstyle.api.TokenTypes;
 29  
 
 30  
 /**
 31  
  * Restricts the number of statements per line to one.
 32  
  * <p>
 33  
  *     Rationale: It's very difficult to read multiple statements on one line.
 34  
  * </p>
 35  
  * <p>
 36  
  *     In the Java programming language, statements are the fundamental unit of
 37  
  *     execution. All statements except blocks are terminated by a semicolon.
 38  
  *     Blocks are denoted by open and close curly braces.
 39  
  * </p>
 40  
  * <p>
 41  
  *     OneStatementPerLineCheck checks the following types of statements:
 42  
  *     variable declaration statements, empty statements, assignment statements,
 43  
  *     expression statements, increment statements, object creation statements,
 44  
  *     'for loop' statements, 'break' statements, 'continue' statements,
 45  
  *     'return' statements, import statements.
 46  
  * </p>
 47  
  * <p>
 48  
  *     The following examples will be flagged as a violation:
 49  
  * </p>
 50  
  * <pre>
 51  
  *     //Each line causes violation:
 52  
  *     int var1; int var2;
 53  
  *     var1 = 1; var2 = 2;
 54  
  *     int var1 = 1; int var2 = 2;
 55  
  *     var1++; var2++;
 56  
  *     Object obj1 = new Object(); Object obj2 = new Object();
 57  
  *     import java.io.EOFException; import java.io.BufferedReader;
 58  
  *     ;; //two empty statements on the same line.
 59  
  *
 60  
  *     //Multi-line statements:
 61  
  *     int var1 = 1
 62  
  *     ; var2 = 2; //violation here
 63  
  *     int o = 1, p = 2,
 64  
  *     r = 5; int t; //violation here
 65  
  * </pre>
 66  
  *
 67  
  * @author Alexander Jesse
 68  
  * @author Oliver Burn
 69  
  * @author Andrei Selkin
 70  
  */
 71  
 @FileStatefulCheck
 72  13
 public final class OneStatementPerLineCheck extends AbstractCheck {
 73  
 
 74  
     /**
 75  
      * A key is pointing to the warning message text in "messages.properties"
 76  
      * file.
 77  
      */
 78  
     public static final String MSG_KEY = "multiple.statements.line";
 79  
 
 80  
     /**
 81  
      * Counts number of semicolons in nested lambdas.
 82  
      */
 83  13
     private final Deque<Integer> countOfSemiInLambda = new ArrayDeque<>();
 84  
 
 85  
     /**
 86  
      * Hold the line-number where the last statement ended.
 87  
      */
 88  13
     private int lastStatementEnd = -1;
 89  
 
 90  
     /**
 91  
      * Hold the line-number where the last 'for-loop' statement ended.
 92  
      */
 93  13
     private int forStatementEnd = -1;
 94  
 
 95  
     /**
 96  
      * The for-header usually has 3 statements on one line, but THIS IS OK.
 97  
      */
 98  
     private boolean inForHeader;
 99  
 
 100  
     /**
 101  
      * Holds if current token is inside lambda.
 102  
      */
 103  
     private boolean isInLambda;
 104  
 
 105  
     /**
 106  
      * Hold the line-number where the last lambda statement ended.
 107  
      */
 108  13
     private int lambdaStatementEnd = -1;
 109  
 
 110  
     @Override
 111  
     public int[] getDefaultTokens() {
 112  18
         return getRequiredTokens();
 113  
     }
 114  
 
 115  
     @Override
 116  
     public int[] getAcceptableTokens() {
 117  6
         return getRequiredTokens();
 118  
     }
 119  
 
 120  
     @Override
 121  
     public int[] getRequiredTokens() {
 122  42
         return new int[] {
 123  
             TokenTypes.SEMI,
 124  
             TokenTypes.FOR_INIT,
 125  
             TokenTypes.FOR_ITERATOR,
 126  
             TokenTypes.LAMBDA,
 127  
         };
 128  
     }
 129  
 
 130  
     @Override
 131  
     public void beginTree(DetailAST rootAST) {
 132  5
         inForHeader = false;
 133  5
         lastStatementEnd = -1;
 134  5
         forStatementEnd = -1;
 135  5
         isInLambda = false;
 136  5
     }
 137  
 
 138  
     @Override
 139  
     public void visitToken(DetailAST ast) {
 140  189
         switch (ast.getType()) {
 141  
             case TokenTypes.SEMI:
 142  151
                 checkIfSemicolonIsInDifferentLineThanPrevious(ast);
 143  151
                 break;
 144  
             case TokenTypes.FOR_ITERATOR:
 145  11
                 forStatementEnd = ast.getLineNo();
 146  11
                 break;
 147  
             case TokenTypes.LAMBDA:
 148  16
                 isInLambda = true;
 149  16
                 countOfSemiInLambda.push(0);
 150  16
                 break;
 151  
             default:
 152  11
                 inForHeader = true;
 153  
                 break;
 154  
         }
 155  189
     }
 156  
 
 157  
     @Override
 158  
     public void leaveToken(DetailAST ast) {
 159  189
         switch (ast.getType()) {
 160  
             case TokenTypes.SEMI:
 161  151
                 lastStatementEnd = ast.getLineNo();
 162  151
                 forStatementEnd = -1;
 163  151
                 lambdaStatementEnd = -1;
 164  151
                 break;
 165  
             case TokenTypes.FOR_ITERATOR:
 166  11
                 inForHeader = false;
 167  11
                 break;
 168  
             case TokenTypes.LAMBDA:
 169  16
                 countOfSemiInLambda.pop();
 170  16
                 if (countOfSemiInLambda.isEmpty()) {
 171  13
                     isInLambda = false;
 172  
                 }
 173  16
                 lambdaStatementEnd = ast.getLineNo();
 174  16
                 break;
 175  
             default:
 176  
                 break;
 177  
         }
 178  189
     }
 179  
 
 180  
     /**
 181  
      * Checks if given semicolon is in different line than previous.
 182  
      * @param ast semicolon to check
 183  
      */
 184  
     private void checkIfSemicolonIsInDifferentLineThanPrevious(DetailAST ast) {
 185  151
         DetailAST currentStatement = ast;
 186  151
         final boolean hasResourcesPrevSibling =
 187  151
                 currentStatement.getPreviousSibling() != null
 188  148
                         && currentStatement.getPreviousSibling().getType() == TokenTypes.RESOURCES;
 189  151
         if (!hasResourcesPrevSibling && isMultilineStatement(currentStatement)) {
 190  25
             currentStatement = ast.getPreviousSibling();
 191  
         }
 192  151
         if (isInLambda) {
 193  22
             int countOfSemiInCurrentLambda = countOfSemiInLambda.pop();
 194  22
             countOfSemiInCurrentLambda++;
 195  22
             countOfSemiInLambda.push(countOfSemiInCurrentLambda);
 196  22
             if (!inForHeader && countOfSemiInCurrentLambda > 1
 197  6
                     && isOnTheSameLine(currentStatement,
 198  
                     lastStatementEnd, forStatementEnd,
 199  
                     lambdaStatementEnd)) {
 200  3
                 log(ast, MSG_KEY);
 201  
             }
 202  22
         }
 203  129
         else if (!inForHeader && isOnTheSameLine(currentStatement, lastStatementEnd,
 204  
                 forStatementEnd, lambdaStatementEnd)) {
 205  18
             log(ast, MSG_KEY);
 206  
         }
 207  151
     }
 208  
 
 209  
     /**
 210  
      * Checks whether two statements are on the same line.
 211  
      * @param ast token for the current statement.
 212  
      * @param lastStatementEnd the line-number where the last statement ended.
 213  
      * @param forStatementEnd the line-number where the last 'for-loop'
 214  
      *                        statement ended.
 215  
      * @param lambdaStatementEnd the line-number where the last lambda
 216  
      *                        statement ended.
 217  
      * @return true if two statements are on the same line.
 218  
      */
 219  
     private static boolean isOnTheSameLine(DetailAST ast, int lastStatementEnd,
 220  
                                            int forStatementEnd, int lambdaStatementEnd) {
 221  230
         return lastStatementEnd == ast.getLineNo() && forStatementEnd != ast.getLineNo()
 222  27
                 && lambdaStatementEnd != ast.getLineNo();
 223  
     }
 224  
 
 225  
     /**
 226  
      * Checks whether statement is multiline.
 227  
      * @param ast token for the current statement.
 228  
      * @return true if one statement is distributed over two or more lines.
 229  
      */
 230  
     private static boolean isMultilineStatement(DetailAST ast) {
 231  
         final boolean multiline;
 232  147
         if (ast.getPreviousSibling() == null) {
 233  3
             multiline = false;
 234  
         }
 235  
         else {
 236  144
             final DetailAST prevSibling = ast.getPreviousSibling();
 237  144
             multiline = prevSibling.getLineNo() != ast.getLineNo()
 238  26
                     && ast.getParent() != null;
 239  
         }
 240  147
         return multiline;
 241  
     }
 242  
 }