Checkstyle: Fine-tune checks, fix some violations, add IntelliJ Checkstyle plugin config

- Fine-tune some of the checks to be more generally applicable
- Fix violations except in code that is planned to be changed soon
- Commit IntelliJ's checkstyle-idea.xml plugin config so that the right file and Checkstyle version are used out of the box

Author: ljacqu

.checkstyle.xml

@@ -214,10 +214,6 @@
         <module name="TypeName" />
 
         <!-- Regexp -->
-        <module name="Regexp">
-            <property name="format" value="System\.out"/>
-            <property name="illegalPattern" value="true"/>
-        </module>
 
         <!-- Size violations -->
 
@@ -228,8 +224,14 @@
         <module name="GenericWhitespace" />
         <module name="MethodParamPad" />
         <module name="NoLineWrap" />
-        <module name="NoWhitespaceAfter" />
-        <module name="NoWhitespaceBefore" />
+        <module name="NoWhitespaceAfter">
+            <!-- Override to exclude ARRAY_INIT and to add LITERAL_SYNCHRONIZED, METHOD_REF -->
+            <property name="tokens" value="AT, INC, DEC, UNARY_MINUS, UNARY_PLUS, BNOT, LNOT, DOT, ARRAY_DECLARATOR, INDEX_OP, LITERAL_SYNCHRONIZED, METHOD_REF" />
+        </module>
+        <module name="NoWhitespaceBefore">
+            <!-- Override to exclude ELLIPSIS and to add METHOD_REF -->
+            <property name="tokens" value="COMMA, SEMI, POST_INC, POST_DEC, LABELED_STAT, METHOD_REF" />
+        </module>
         <!-- Checkstyle 8.45: <module name="NoWhitespaceBeforeCaseDefaultColon" /> -->
         <module name="OperatorWrap" />
         <module name="ParenPad" />

.gitignore

@@ -18,6 +18,8 @@ hs_err_pid*
 
 # Ignore IDEA directory
 .idea/*
+!.idea/vcs.xml
+!.idea/checkstyle-idea.xml
 
 # File-based project format:
 *.ipr

.idea/checkstyle-idea.xml

@@ -38,7 +38,7 @@ public void add(@NotNull Property<?> property) {
         final String lastElement = pathElements[pathElements.length - 1];
         if (mapForProperty.containsKey(lastElement)) {
             throw new ConfigMeException("Path at '" + property.getPath() + "' already exists");
-        } else if (pathElements.length > 1 && lastElement.equals("")) {
+        } else if (pathElements.length > 1 && "".equals(lastElement)) {
             throwExceptionForMalformedPath(property.getPath());
         }
         mapForProperty.put(lastElement, property);

src/main/java/ch/jalu/configme/configurationdata/PropertyListBuilder.java

@@ -10,6 +10,11 @@
 import java.util.Objects;
 import java.util.function.IntFunction;
 
+/**
+ * Property whose value is an array of a given type.
+ *
+ * @param <T> the type of the elements in the array
+ */
 public class ArrayProperty<T> extends BaseProperty<T[]> {
 
     private final PropertyType<T> type;

src/main/java/ch/jalu/configme/properties/ArrayProperty.java

@@ -7,6 +7,11 @@
 import ch.jalu.typeresolver.TypeInfo;
 import org.jetbrains.annotations.NotNull;
 
+/**
+ * Property whose value is a bean class.
+ *
+ * @param <T> the bean type
+ */
 public class BeanProperty<T> extends TypeBasedProperty<T> {
 
     public BeanProperty(@NotNull Class<T> beanType, @NotNull String path, @NotNull T defaultValue) {

src/main/java/ch/jalu/configme/properties/BeanProperty.java

@@ -12,6 +12,8 @@
  * <p>
  * Wraps another property with an {@link Optional}: if a property is not present in the property resource,
  * {@link Optional#empty} is returned.
+ *
+ * @param <T> the type of value
  */
 public class OptionalProperty<T> implements Property<Optional<T>> {
 

src/main/java/ch/jalu/configme/properties/OptionalProperty.java

@@ -7,6 +7,11 @@
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 
+/**
+ * Property type that maps values to a specific bean class.
+ *
+ * @param <B> the bean type
+ */
 public class BeanPropertyType<B> implements PropertyType<B> {
 
     private final TypeInfo beanType;

src/main/java/ch/jalu/configme/properties/types/BeanPropertyType.java

@@ -5,6 +5,11 @@
 import java.util.List;
 import java.util.Set;
 
+/**
+ * A property reader provides values from a resource (e.g. a YAML file) based on whose data the values of properties
+ * are determined. Property readers typically provide a snapshot of the file's contents, i.e. their values are not
+ * updated if the underlying file changes.
+ */
 public interface PropertyReader {
 
     /**

src/main/java/ch/jalu/configme/resource/PropertyReader.java

@@ -25,6 +25,9 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+/**
+ * Property resource based on a YAML file.
+ */
 public class YamlFileResource implements PropertyResource {
 
     private final Path path;

src/main/java/ch/jalu/configme/resource/YamlFileResource.java

@@ -8,6 +8,9 @@
 import java.nio.charset.StandardCharsets;
 import java.util.function.ToIntFunction;
 
+/**
+ * Options for {@link YamlFileResource} to configure reading and writing YAML.
+ */
 public class YamlFileResourceOptions {
 
     private final @NotNull Charset charset;
@@ -49,11 +52,16 @@ public int getIndentationSize() {
         return numberOfLinesBeforeFunction;
     }
 
+    /**
+     * Builder to create YAML file resource options.
+     */
     public static class Builder {
 
+        private static final int DEFAULT_INDENTATION_SIZE = 4;
+
         private Charset charset;
         private ToIntFunction<PathElement> numberOfLinesBeforeFunction;
-        private int indentationSize = 4;
+        private int indentationSize = DEFAULT_INDENTATION_SIZE;
 
         public @NotNull Builder charset(@Nullable Charset charset) {
             this.charset = charset;

src/main/java/ch/jalu/configme/resource/YamlFileResourceOptions.java

@@ -32,6 +32,8 @@
  */
 public class SettingsHolderClassValidator {
 
+    private static final int DEFAULT_MAX_COMMENTS_LENGTH = 90;
+
     // ---- Main validation methods (with default settings)
 
     /**
@@ -62,7 +64,7 @@ public void validate(@NotNull Iterable<Class<? extends SettingsHolder>> settingH
         // no properties have overlapping paths
         ConfigurationData configurationData = createConfigurationData(settingHolders);
         validateHasCommentOnEveryProperty(configurationData, null);
-        validateCommentLengthsAreWithinBounds(configurationData, null, 90);
+        validateCommentLengthsAreWithinBounds(configurationData, null, DEFAULT_MAX_COMMENTS_LENGTH);
         validateHasAllEnumEntriesInComment(configurationData, null);
     }