Equality cleanup:

- replaced all `a.equals(b)` with `a == b`;
- replaced all `a.eq(null)` with `a == null`;
- replaced all `a.ne(null)` with `a != null`;
- replaced all `a.eq(Null) with `a.isNull`;
- replaced some `string == ""` with `string.isEmpty`;
- removed some spurious braces.

jvm/src/test/scala/scala/xml/XMLTest.scala

@@ -2,8 +2,8 @@ package scala.xml
 
 import org.junit.{Test => UnitTest}
 import org.junit.Assert.{assertEquals, assertFalse, assertNull, assertThrows, assertTrue}
-import java.io.StringWriter
-import java.io.ByteArrayOutputStream
+import java.io.{ByteArrayInputStream, ByteArrayOutputStream, InputStreamReader, IOException, ObjectInputStream,
+  ObjectOutputStream, OutputStreamWriter, PrintStream, StringWriter}
 import java.net.URL
 import scala.xml.dtd.{DocType, PublicID}
 import scala.xml.parsing.ConstructingParser
@@ -177,26 +177,26 @@ class XMLTestJVM {
     </entry>""", f("a,b,c").toString)
 
   object Serialize {
-    @throws(classOf[java.io.IOException])
+    @throws(classOf[IOException])
     def write[A](o: A): Array[Byte] = {
       val ba: ByteArrayOutputStream = new ByteArrayOutputStream(512)
-      val out: java.io.ObjectOutputStream = new java.io.ObjectOutputStream(ba)
+      val out: ObjectOutputStream = new ObjectOutputStream(ba)
       out.writeObject(o)
       out.close()
       ba.toByteArray
     }
-    @throws(classOf[java.io.IOException])
+    @throws(classOf[IOException])
     @throws(classOf[ClassNotFoundException])
     def read[A](buffer: Array[Byte]): A = {
-      val in: java.io.ObjectInputStream =
-        new java.io.ObjectInputStream(new java.io.ByteArrayInputStream(buffer))
+      val in: ObjectInputStream =
+        new ObjectInputStream(new ByteArrayInputStream(buffer))
       in.readObject().asInstanceOf[A]
     }
     def check[A, B](x: A, y: B): Unit = {
       // println("x = " + x)
       // println("y = " + y)
-      // println("x equals y: " + (x equals y) + ", y equals x: " + (y equals x))
-      assertTrue(x.equals(y) && y.equals(x))
+      // println("x == y: " + (x == y) + ", y == x: " + (y == x))
+      assertTrue(x == y && y == x)
       // println()
     }
   }
@@ -296,14 +296,14 @@ class XMLTestJVM {
     // scala.xml.XML.save("foo.xml", xml)
     // scala.xml.XML.loadFile("foo.xml").toString
 
-    val outputStream: java.io.ByteArrayOutputStream = new java.io.ByteArrayOutputStream
-    val streamWriter: java.io.OutputStreamWriter = new java.io.OutputStreamWriter(outputStream, "UTF-8")
+    val outputStream: ByteArrayOutputStream = new ByteArrayOutputStream
+    val streamWriter: OutputStreamWriter = new OutputStreamWriter(outputStream, "UTF-8")
 
     XML.write(streamWriter, xml, XML.encoding, xmlDecl = false, null)
     streamWriter.flush()
 
-    val inputStream: java.io.ByteArrayInputStream = new java.io.ByteArrayInputStream(outputStream.toByteArray)
-    val streamReader: java.io.InputStreamReader = new java.io.InputStreamReader(inputStream, XML.encoding)
+    val inputStream: ByteArrayInputStream = new ByteArrayInputStream(outputStream.toByteArray)
+    val streamReader: InputStreamReader = new InputStreamReader(inputStream, XML.encoding)
 
     assertEquals(xml.toString, XML.load(streamReader).toString)
   }
@@ -492,8 +492,6 @@ class XMLTestJVM {
 
   @UnitTest
   def dontLoop(): Unit = {
-    import java.io.{ Console => _, _ }
-
     val xml: String = "<!DOCTYPE xmeml SYSTEM 'uri'> <xmeml> <sequence> </sequence> </xmeml> "
     val sink: PrintStream = new PrintStream(new ByteArrayOutputStream())
     Console.withOut(sink) {
@@ -1026,7 +1024,7 @@ class XMLTestJVM {
 
   def toSource(s: String): scala.io.Source = new scala.io.Source {
     override val iter: Iterator[Char] = s.iterator
-    override def reportError(pos: Int, msg: String, out: java.io.PrintStream = Console.err): Unit = ()
+    override def reportError(pos: Int, msg: String, out: PrintStream = Console.err): Unit = ()
   }
 
   @UnitTest

shared/src/main/scala/scala/xml/Attribute.scala

@@ -81,15 +81,13 @@ trait Attribute extends MetaData {
   }
 
   /** Returns an iterator on attributes */
-  override def iterator: Iterator[MetaData] = {
+  override def iterator: Iterator[MetaData] =
     if (value == null) next.iterator
     else Iterator.single(this) ++ next.iterator
-  }
 
-  override def size: Int = {
+  override def size: Int =
     if (value == null) next.size
     else 1 + next.size
-  }
 
   /**
    * Appends string representation of only this attribute to stringbuffer.

shared/src/main/scala/scala/xml/Comment.scala

@@ -29,12 +29,11 @@ case class Comment(commentText: String) extends SpecialNode {
   final override def doCollectNamespaces: Boolean = false
   final override def doTransform: Boolean = false
 
-  if (commentText.contains("--")) {
+  if (commentText.contains("--"))
     throw new IllegalArgumentException(s"""text contains "--"""")
-  }
-  if (commentText.nonEmpty && commentText.charAt(commentText.length - 1) == '-') {
+
+  if (commentText.nonEmpty && commentText.charAt(commentText.length - 1) == '-')
     throw new IllegalArgumentException("The final character of a XML comment may not be '-'. See https://www.w3.org/TR/xml11//#IDA5CES")
-  }
 
   /**
    * Appends &quot;<!-- text -->&quot; to this string buffer.

shared/src/main/scala/scala/xml/Equality.scala

@@ -61,18 +61,13 @@ object Equality {
     case x: NodeSeq if x.length == 1 => x2 == x(0)
     case _                           => false
   }
-  def compareBlithely(x1: AnyRef, x2: AnyRef): Boolean = {
-    if (x1 == null || x2 == null)
-      return x1.eq(x2)
-
-    x2 match {
+  def compareBlithely(x1: AnyRef, x2: AnyRef): Boolean =
+    if (x1 == null || x2 == null) x1 == null && x2 == null else x2 match {
       case s: String => compareBlithely(x1, s)
       case n: Node   => compareBlithely(x1, n)
       case _         => false
     }
-  }
 }
-import Equality._
 
 trait Equality extends scala.Equals {
   protected def basisForHashCode: Seq[Any]
@@ -109,10 +104,10 @@ trait Equality extends scala.Equals {
   private def doComparison(other: Any, blithe: Boolean): Boolean = {
     val strictlyEqual: Boolean = other match {
       case x: AnyRef if this.eq(x) => true
-      case x: Equality             => (x canEqual this) && (this strict_== x)
+      case x: Equality             => x.canEqual(this) && this.strict_==(x)
       case _                       => false
     }
 
-    strictlyEqual || (blithe && compareBlithely(this, asRef(other)))
+    strictlyEqual || (blithe && Equality.compareBlithely(this, Equality.asRef(other)))
   }
 }

shared/src/main/scala/scala/xml/MetaData.scala

@@ -29,28 +29,27 @@ object MetaData {
    */
   @tailrec
   def concatenate(attribs: MetaData, new_tail: MetaData): MetaData =
-    if (attribs.eq(Null)) new_tail
+    if (attribs.isNull) new_tail
     else concatenate(attribs.next, attribs.copy(new_tail))
 
   /**
    * returns normalized MetaData, with all duplicates removed and namespace prefixes resolved to
    *  namespace URIs via the given scope.
    */
   def normalize(attribs: MetaData, scope: NamespaceBinding): MetaData = {
-    def iterate(md: MetaData, normalized_attribs: MetaData, set: Set[String]): MetaData = {
-      if (md.eq(Null)) {
+    def iterate(md: MetaData, normalized_attribs: MetaData, set: Set[String]): MetaData =
+      if (md.isNull) {
         normalized_attribs
-      } else if (md.value.eq(null)) {
+      } else if (md.value == null)
         iterate(md.next, normalized_attribs, set)
-      } else {
+      else {
         val key: String = getUniversalKey(md, scope)
-        if (set(key)) {
+        if (set(key))
           iterate(md.next, normalized_attribs, set)
-        } else {
+        else
           md.copy(iterate(md.next, normalized_attribs, set + key))
-        }
       }
-    }
+
     iterate(attribs, Null, Set())
   }
 
@@ -85,7 +84,9 @@ abstract class MetaData
   extends AbstractIterable[MetaData]
   with Iterable[MetaData]
   with Equality
-  with Serializable {
+  with Serializable
+{
+  private[xml] def isNull: Boolean = this.eq(Null)
 
   /**
    * Updates this MetaData with the MetaData given as argument. All attributes that occur in updates

shared/src/main/scala/scala/xml/NamespaceBinding.scala

@@ -29,8 +29,8 @@ case class NamespaceBinding(prefix: String, uri: String, parent: NamespaceBindin
   if (prefix == "")
     throw new IllegalArgumentException("zero length prefix not allowed")
 
-  def getURI(_prefix: String): String =
-    if (prefix == _prefix) uri else parent.getURI(_prefix)
+  def getURI(prefix: String): String =
+    if (this.prefix == prefix) uri else parent.getURI(prefix)
 
   /**
    * Returns some prefix that is mapped to the URI.
@@ -39,8 +39,8 @@ case class NamespaceBinding(prefix: String, uri: String, parent: NamespaceBindin
    * @return the prefix that is mapped to the input URI, or null
    * if no prefix is mapped to the URI.
    */
-  def getPrefix(_uri: String): String =
-    if (_uri == uri) prefix else parent.getPrefix(_uri)
+  def getPrefix(uri: String): String =
+    if (uri == this.uri) prefix else parent.getPrefix(uri)
 
   override def toString: String = Utility.sbToString(buildString(_, TopScope))
 
@@ -72,9 +72,8 @@ case class NamespaceBinding(prefix: String, uri: String, parent: NamespaceBindin
 
   def buildString(stop: NamespaceBinding): String = Utility.sbToString(buildString(_, stop))
 
-  def buildString(sb: StringBuilder, stop: NamespaceBinding): Unit = {
+  def buildString(sb: StringBuilder, stop: NamespaceBinding): Unit =
     shadowRedefined(stop).doBuildString(sb, stop)
-  }
 
   private def doBuildString(sb: StringBuilder, stop: NamespaceBinding): Unit = {
     if (List(null, stop, TopScope).contains(this)) return

shared/src/main/scala/scala/xml/Node.scala

@@ -82,7 +82,7 @@ abstract class Node extends NodeSeq {
    * @return    the namespace if `scope != null` and prefix was
    *            found, else `null`
    */
-  def getNamespace(pre: String): String = if (scope.eq(null)) null else scope.getURI(pre)
+  def getNamespace(pre: String): String = if (scope == null) null else scope.getURI(pre)
 
   /**
    * Convenience method, looks up an unprefixed attribute in attributes of this node.
@@ -125,7 +125,7 @@ abstract class Node extends NodeSeq {
   /**
    * Children which do not stringify to "" (needed for equality)
    */
-  def nonEmptyChildren: Seq[Node] = child.filterNot(_.toString == "")
+  def nonEmptyChildren: Seq[Node] = child.filterNot(_.toString.isEmpty)
 
   /**
    * Descendant axis (all descendants of this node, not including node itself)

shared/src/main/scala/scala/xml/NodeSeq.scala

@@ -103,7 +103,7 @@ abstract class NodeSeq extends AbstractSeq[Node] with immutable.Seq[Node] with S
           val i: Int = that.indexOf('}')
           if (i == -1) fail
           val (uri: String, key: String) = (that.substring(2, i), that.substring(i + 1, that.length))
-          if (uri == "" || key == "") fail
+          if (uri.isEmpty || key.isEmpty) fail
           else y.attribute(uri, key)
         } else y.attribute(that.drop(1))
 

shared/src/main/scala/scala/xml/PrefixedAttribute.scala

@@ -28,13 +28,15 @@ class PrefixedAttribute(
   override val pre: String,
   override val key: String,
   override val value: Seq[Node],
-  val next1: MetaData)
-  extends Attribute {
-  override val next: MetaData = if (value.ne(null)) next1 else next1.remove(key)
+  val next1: MetaData
+)
+  extends Attribute
+{
+  override val next: MetaData = if (value != null) next1 else next1.remove(key)
 
   /** same as this(pre, key, Text(value), next), or no attribute if value is null */
   def this(pre: String, key: String, value: String, next: MetaData) =
-    this(pre, key, if (value.ne(null)) Text(value) else null: NodeSeq, next)
+    this(pre, key, if (value != null) Text(value) else null: NodeSeq, next)
 
   /** same as this(pre, key, value.get, next), or no attribute if value is None */
   def this(pre: String, key: String, value: Option[Seq[Node]], next: MetaData) =
@@ -56,12 +58,11 @@ class PrefixedAttribute(
   /**
    * gets attribute value of qualified (prefixed) attribute with given key
    */
-  override def apply(namespace: String, scope: NamespaceBinding, key: String): Seq[Node] = {
+  override def apply(namespace: String, scope: NamespaceBinding, key: String): Seq[Node] =
     if (key == this.key && scope.getURI(pre) == namespace)
       value
     else
       next(namespace, scope, key)
-  }
 }
 
 object PrefixedAttribute {

shared/src/main/scala/scala/xml/PrettyPrinter.scala

@@ -150,7 +150,7 @@ class PrettyPrinter(width: Int, step: Int, minimizeEmpty: Boolean) {
 
   protected def traverse(node: Node, pscope: NamespaceBinding, ind: Int): Unit = node match {
 
-    case Text(s) if s.trim == "" =>
+    case Text(s) if s.trim.isEmpty =>
 
     case _: Atom[_] | _: Comment | _: EntityRef | _: ProcInstr =>
       makeBox(ind, node.toString.trim)
@@ -163,18 +163,17 @@ class PrettyPrinter(width: Int, step: Int, minimizeEmpty: Boolean) {
         if (doPreserve(node)) sb.toString
         else TextBuffer.fromString(sb.toString).toText(0).data
       }
-      if (childrenAreLeaves(node) && fits(test)) {
+      if (childrenAreLeaves(node) && fits(test))
         makeBox(ind, test)
-      } else {
+      else {
         val ((stg: String, len2: Int), etg: String) =
           if (node.child.isEmpty && minimizeEmpty) {
             // force the tag to be self-closing
             val firstAttribute: Int = test.indexOf(' ')
             val firstBreak: Int = if (firstAttribute != -1) firstAttribute else test.lastIndexOf('/')
             ((test, firstBreak), "")
-          } else {
+          } else
             (startTag(node, pscope), endTag(node))
-          }
 
         if (stg.length < width - cur) { // start tag fits
           makeBox(ind, stg)
@@ -221,9 +220,7 @@ class PrettyPrinter(width: Int, step: Int, minimizeEmpty: Boolean) {
    * @param n    the node to be serialized
    * @param sb   the stringbuffer to append to
    */
-  def format(n: Node, sb: StringBuilder): Unit = { // entry point
-    format(n, TopScope, sb)
-  }
+  def format(n: Node, sb: StringBuilder): Unit = format(n, TopScope, sb) // entry point
 
   def format(n: Node, pscope: NamespaceBinding, sb: StringBuilder): Unit = { // entry point
     var lastwasbreak: Boolean = false

shared/src/main/scala/scala/xml/ProcInstr.scala

@@ -39,8 +39,6 @@ case class ProcInstr(target: String, proctext: String) extends SpecialNode {
    * appends "<?" target (" "+text)?+"?>"
    *  to this stringbuffer.
    */
-  override def buildString(sb: StringBuilder): StringBuilder = {
-    val textStr: String = if (proctext == "") "" else s" $proctext"
-    sb.append(s"<?$target$textStr?>")
-  }
+  override def buildString(sb: StringBuilder): StringBuilder =
+    sb.append(s"<?$target${if (proctext.isEmpty) "" else s" $proctext"}?>")
 }

shared/src/main/scala/scala/xml/TopScope.scala

@@ -20,13 +20,11 @@ package xml
  */
 object TopScope extends NamespaceBinding(null, null, null) {
 
-  import XML.{xml, namespace}
-
   override def getURI(prefix1: String): String =
-    if (prefix1 == xml) namespace else null
+    if (prefix1 == XML.xml) XML.namespace else null
 
   override def getPrefix(uri1: String): String =
-    if (uri1 == namespace) xml else null
+    if (uri1 == XML.namespace) XML.xml else null
 
   override def toString: String = ""
 

shared/src/main/scala/scala/xml/UnprefixedAttribute.scala

@@ -24,14 +24,16 @@ import scala.collection.Seq
 class UnprefixedAttribute(
   override val key: String,
   override val value: Seq[Node],
-  next1: MetaData)
-  extends Attribute {
+  next1: MetaData
+)
+  extends Attribute
+{
   final override val pre: scala.Null = null
-  override val next: MetaData = if (value.ne(null)) next1 else next1.remove(key)
+  override val next: MetaData = if (value != null) next1 else next1.remove(key)
 
   /** same as this(key, Text(value), next), or no attribute if value is null */
   def this(key: String, value: String, next: MetaData) =
-    this(key, if (value.ne(null)) Text(value) else null: NodeSeq, next)
+    this(key, if (value != null) Text(value) else null: NodeSeq, next)
 
   /** same as this(key, value.get, next), or no attribute if value is None */
   def this(key: String, value: Option[Seq[Node]], next: MetaData) =