MethodLengthCheck.java
///////////////////////////////////////////////////////////////////////////////////////////////
// checkstyle: Checks Java source code and other text files for adherence to a set of rules.
// Copyright (C) 2001-2022 the original author or authors.
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
///////////////////////////////////////////////////////////////////////////////////////////////
package com.puppycrawl.tools.checkstyle.checks.sizes;
import java.util.ArrayDeque;
import java.util.BitSet;
import java.util.Deque;
import java.util.Objects;
import java.util.stream.Stream;
import com.puppycrawl.tools.checkstyle.StatelessCheck;
import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
import com.puppycrawl.tools.checkstyle.api.DetailAST;
import com.puppycrawl.tools.checkstyle.api.TokenTypes;
import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
/**
* <p>
* Checks for long methods and constructors.
* </p>
* <p>
* Rationale: If a method becomes very long it is hard to understand.
* Therefore, long methods should usually be refactored into several
* individual methods that focus on a specific task.
* </p>
* <ul>
* <li>
* Property {@code max} - Specify the maximum number of lines allowed.
* Type is {@code int}.
* Default value is {@code 150}.
* </li>
* <li>
* Property {@code countEmpty} - Control whether to count empty lines and comments.
* Type is {@code boolean}.
* Default value is {@code true}.
* </li>
* <li>
* Property {@code tokens} - tokens to check
* Type is {@code java.lang.String[]}.
* Validation type is {@code tokenSet}.
* Default value is:
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#METHOD_DEF">
* METHOD_DEF</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#CTOR_DEF">
* CTOR_DEF</a>,
* <a href="https://checkstyle.org/apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html#COMPACT_CTOR_DEF">
* COMPACT_CTOR_DEF</a>.
* </li>
* </ul>
* <p>
* To configure the check:
* </p>
* <pre>
* <module name="MethodLength"/>
* </pre>
* <p>
* Example:
* </p>
* <pre>
* public class MyClass {
* public MyClass() { // constructor (line 1)
* /* line 2
* ...
* line 150 */
* } // line 151, violation, as it is over 150
*
* public void firstExample() { // line 1
*
* // line 3
* System.out.println("line 4");
* /* line 5
* line 6 */
* } // line 7, OK, as it is less than 150
*
* public void secondExample() { // line 1
* // line 2
* System.out.println("line 3");
*
* /* line 5
* ...
* line 150 */
* } // line 151, violation, as it is over 150
* }
* </pre>
* <p>
* To configure the check so that it accepts methods with at most 4 lines:
* </p>
* <pre>
* <module name="MethodLength">
* <property name="tokens" value="METHOD_DEF"/>
* <property name="max" value="4"/>
* </module>
* </pre>
* <p>
* Example:
* </p>
* <pre>
* public class MyTest {
* public MyTest() { // constructor (line 1)
* int var1 = 2; // line 2
* int var2 = 4; // line 3
* int sum = var1 + var2; // line 4
* } // line 5, OK, constructor is not mentioned in the tokens
*
* public void firstMethod() { // line 1
* // comment (line 2)
* System.out.println("line 3");
* } // line 4, OK, as it allows at most 4 lines
*
* public void secondMethod() { // line 1
* int index = 0; // line 2
* if (index < 5) { // line 3
* index++; // line 4
* } // line 5
* } // line 6, violation, as it is over 4 lines
*
* public void thirdMethod() { // line 1
*
* // comment (line 3)
* System.out.println("line 4");
* } // line 5, violation, as it is over 4 lines
* }
* </pre>
* <p>
* To configure the check so that it accepts methods with at most 4 lines,
* not counting empty lines and comments:
* </p>
* <pre>
* <module name="MethodLength">
* <property name="tokens" value="METHOD_DEF"/>
* <property name="max" value="4"/>
* <property name="countEmpty" value="false"/>
* </module>
* </pre>
* <p>
* Example:
* </p>
* <pre>
* public class MyTest {
* public MyTest() { // constructor (line 1)
* int var1 = 2; // line 2
* int var2 = 4; // line 3
* int sum = var1 + var2; // line 4
* } // line 5, OK, constructor is not mentioned in the tokens
*
* public void firstMethod() { // line 1
* // comment - not counted as line
* System.out.println("line 2");
* } // line 3, OK, as it allows at most 4 lines
*
* public void secondMethod() { // line 1
* int index = 0; // line 2
* if (index < 5) { // line 3
* index++; // line 4
* } // line 5
* } // line 6, violation, as it is over 4 lines
*
* public void thirdMethod() { // line 1
*
* // comment - not counted as line
* System.out.println("line 2");
* } // line 3, OK, as it allows at most 4 lines
* }
* </pre>
* <p>
* Parent is {@code com.puppycrawl.tools.checkstyle.TreeWalker}
* </p>
* <p>
* Violation Message Keys:
* </p>
* <ul>
* <li>
* {@code maxLen.method}
* </li>
* </ul>
*
* @since 3.0
*/
@StatelessCheck
public class MethodLengthCheck extends AbstractCheck {
/**
* A key is pointing to the warning message text in "messages.properties"
* file.
*/
public static final String MSG_KEY = "maxLen.method";
/** Default maximum number of lines. */
private static final int DEFAULT_MAX_LINES = 150;
/** Control whether to count empty lines and comments. */
private boolean countEmpty = true;
/** Specify the maximum number of lines allowed. */
private int max = DEFAULT_MAX_LINES;
@Override
public int[] getDefaultTokens() {
return getAcceptableTokens();
}
@Override
public int[] getAcceptableTokens() {
return new int[] {
TokenTypes.METHOD_DEF,
TokenTypes.CTOR_DEF,
TokenTypes.COMPACT_CTOR_DEF,
};
}
@Override
public int[] getRequiredTokens() {
return CommonUtil.EMPTY_INT_ARRAY;
}
@Override
public void visitToken(DetailAST ast) {
final DetailAST openingBrace = ast.findFirstToken(TokenTypes.SLIST);
if (openingBrace != null) {
final int length;
if (countEmpty) {
final DetailAST closingBrace = openingBrace.findFirstToken(TokenTypes.RCURLY);
length = getLengthOfBlock(openingBrace, closingBrace);
}
else {
length = countUsedLines(openingBrace);
}
if (length > max) {
final String methodName = ast.findFirstToken(TokenTypes.IDENT).getText();
log(ast, MSG_KEY, length, max, methodName);
}
}
}
/**
* Returns length of code.
*
* @param openingBrace block opening brace
* @param closingBrace block closing brace
* @return number of lines with code for current block
*/
private static int getLengthOfBlock(DetailAST openingBrace, DetailAST closingBrace) {
final int startLineNo = openingBrace.getLineNo();
final int endLineNo = closingBrace.getLineNo();
return endLineNo - startLineNo + 1;
}
/**
* Count number of used code lines without comments.
*
* @param ast start ast
* @return number of used lines of code
*/
private static int countUsedLines(DetailAST ast) {
final Deque<DetailAST> nodes = new ArrayDeque<>();
nodes.add(ast);
final BitSet usedLines = new BitSet();
final int startLineNo = ast.getLineNo();
while (!nodes.isEmpty()) {
final DetailAST node = nodes.removeFirst();
final int lineIndex = node.getLineNo() - startLineNo;
// text block requires special treatment,
// since it is the only non-comment token that can span more than one line
if (node.getType() == TokenTypes.TEXT_BLOCK_LITERAL_BEGIN) {
final int endLineIndex = node.getLastChild().getLineNo() - startLineNo;
usedLines.set(lineIndex, endLineIndex + 1);
}
else {
usedLines.set(lineIndex);
Stream.iterate(
node.getLastChild(), Objects::nonNull, DetailAST::getPreviousSibling
).forEach(nodes::addFirst);
}
}
return usedLines.cardinality();
}
/**
* Setter to specify the maximum number of lines allowed.
*
* @param length the maximum length of a method.
*/
public void setMax(int length) {
max = length;
}
/**
* Setter to control whether to count empty lines and comments.
*
* @param countEmpty whether to count empty and comments.
*/
public void setCountEmpty(boolean countEmpty) {
this.countEmpty = countEmpty;
}
}