some code cleanup

src/main/kotlin/nl/knaw/huygens/tei/DelegatingVisitor.kt

@@ -48,23 +48,22 @@ open class DelegatingVisitor<T : Context>(context: T) : DefaultVisitor() {
         get() = context.result
 
     fun setTextHandler(handler: TextHandler<T>) {
-        textHandler = Preconditions.checkNotNull(handler)
+        textHandler = handler
     }
 
     fun setCommentHandler(handler: CommentHandler<T>) {
-        commentHandler = Preconditions.checkNotNull(handler)
+        commentHandler = handler
     }
 
     fun setProcessingInstructionHandler(handler: ProcessingInstructionHandler<T>) {
-        processingInstructionHandler = Preconditions.checkNotNull(handler)
+        processingInstructionHandler = handler
     }
 
     fun setDefaultElementHandler(handler: ElementHandler<T>) {
-        defaultHandler = Preconditions.checkNotNull(handler)
+        defaultHandler = handler
     }
 
     fun addElementHandler(handler: ElementHandler<T>, vararg names: String) {
-        Preconditions.checkNotNull(handler)
         for (name in names) {
             handlers[name] = handler
         }
@@ -93,23 +92,14 @@ open class DelegatingVisitor<T : Context>(context: T) : DefaultVisitor() {
     }
 
     // --- Visiting ------------------------------------------------------
-    override fun enterElement(element: Element): Traversal {
-        return getElementHandler(element).enterElement(element, context)
-    }
+    override fun enterElement(element: Element): Traversal = getElementHandler(element).enterElement(element, context)
 
-    override fun leaveElement(element: Element): Traversal {
-        return getElementHandler(element).leaveElement(element, context)
-    }
+    override fun leaveElement(element: Element): Traversal = getElementHandler(element).leaveElement(element, context)
 
-    override fun visitText(text: Text): Traversal {
-        return textHandler.visitText(text, context)
-    }
+    override fun visitText(text: Text): Traversal = textHandler.visitText(text, context)
 
-    override fun visitComment(comment: Comment): Traversal {
-        return commentHandler.visitComment(comment, context)
-    }
+    override fun visitComment(comment: Comment): Traversal = commentHandler.visitComment(comment, context)
 
-    override fun visitProcessingInstruction(processingInstruction: ProcessingInstruction): Traversal {
-        return processingInstructionHandler.visitProcessingInstruction(processingInstruction, context)
-    }
+    override fun visitProcessingInstruction(processingInstruction: ProcessingInstruction): Traversal =
+        processingInstructionHandler.visitProcessingInstruction(processingInstruction, context)
 }

src/main/kotlin/nl/knaw/huygens/tei/Element.kt

@@ -148,7 +148,7 @@ class Element @JvmOverloads constructor(// -------------------------------------
 
     fun hasAttribute(key: String): Boolean {
         val value = attributes[key]
-        return (value != null) && (value.isNotEmpty())
+        return !value.isNullOrEmpty()
     }
 
     fun hasAttribute(key: String, value: String): Boolean {

src/main/kotlin/nl/knaw/huygens/tei/TeiException.kt

@@ -32,7 +32,4 @@ class TeiException : Exception {
 
     constructor(format: String, vararg args: Any) : super(String.format(format, *args))
 
-    companion object {
-        private const val serialVersionUID = 1L
-    }
 }

src/main/kotlin/nl/knaw/huygens/tei/handlers/RenderTextHandler.kt

@@ -37,7 +37,6 @@ open class RenderTextHandler<T : Context> : TextHandler<T> {
         return Traversal.NEXT
     }
 
-    protected open fun filterText(content: String): String {
-        return content
-    }
+    protected open fun filterText(content: String): String =
+        content
 }

src/main/kotlin/nl/knaw/huygens/tei/handlers/XmlTextHandler.kt

@@ -25,11 +25,11 @@ import nl.knaw.huygens.tei.Context
 */
 
 class XmlTextHandler<T : Context> : RenderTextHandler<T>() {
-    override fun filterText(text: String): String {
-        val n = text.length
+    override fun filterText(content: String): String {
+        val n = content.length
         val builder = StringBuilder((n * 1.1).toInt())
         for (i in 0 until n) {
-            when (val c = text[i]) {
+            when (val c = content[i]) {
                 '<' -> builder.append("&lt;")
                 '>' -> builder.append("&gt;")
                 '&' -> builder.append("&amp;")

src/main/kotlin/nl/knaw/huygens/tei/xpath/XPathUtil.kt

@@ -71,9 +71,8 @@ object XPathUtil {
     }
 
     @Throws(XPathExpressionException::class)
-    fun evaluate(xpathQuery: String, xml: String): String {
-        return evaluate(xpathQuery, xml, String::class.java)
-    }
+    fun evaluate(xpathQuery: String, xml: String): String =
+        evaluate(xpathQuery, xml, String::class.java)
 
     fun getNamespaceInfo(xml: String): Map<String, String> {
         val namespaces: MutableMap<String, String> = Maps.newIdentityHashMap()

src/test/kotlin/nl/knaw/huygens/tei/DefaultContextTest.kt

@@ -0,0 +1,12 @@
+package nl.knaw.huygens.tei
+
+import kotlin.test.assertEquals
+import org.junit.Test
+
+class DefaultContextTest {
+    @Test
+    fun `result is empty`() {
+        val context = DefaultContext()
+        assertEquals("", context.result)
+    }
+}

src/test/kotlin/nl/knaw/huygens/tei/TeiExceptionTest.kt

@@ -37,4 +37,10 @@ class TeiExceptionTest {
         val e = TeiException("Test %d", 1)
         assertEquals("Test 1", e.message)
     }
+
+    @Test
+    fun testConstructor() {
+        val e = TeiException("Test")
+        assertEquals("Test", e.message)
+    }
 }

src/test/kotlin/nl/knaw/huygens/tei/handlers/XmlTextHandlerTest.kt

@@ -0,0 +1,15 @@
+package nl.knaw.huygens.tei.handlers
+
+import kotlin.test.Test
+import nl.knaw.huygens.tei.DefaultContext
+import nl.knaw.huygens.tei.Text
+
+class XmlTextHandlerTest {
+    @Test
+    fun test() {
+        val handler = XmlTextHandler<DefaultContext>()
+        val context = DefaultContext()
+        handler.visitText(Text("test"), context)
+    }
+}
+