Merge ListUtil into StringUtil; refactor HelpSyntaxHelper + create test

The HelpSyntaxHelper had suppressed warnings for string concatenation within StringBuilder - the point of the StringBuilder is that it is faster when you use it to concatenate many elements. If you still use string concatenation with + within these calls it beats the purpose.
(cherry picked from commit bb00be2)

src/main/java/fr/xephi/authme/command/CommandParts.java

@@ -3,7 +3,6 @@ package fr.xephi.authme.command;
 import java.util.ArrayList;
 import java.util.List;
 
-import fr.xephi.authme.util.ListUtils;
 import fr.xephi.authme.util.StringUtils;
 
 /**
@@ -165,8 +164,8 @@ public class CommandParts {
      *
      * @param other The other reference.
      *
-    
-     * @return The result from zero to above. A negative number will be returned on error. */
+     * @return The result from zero to above. A negative number will be returned on error.
+     */
     public double getDifference(CommandParts other) {
         return getDifference(other, false);
     }
@@ -177,8 +176,8 @@ public class CommandParts {
      * @param other The other reference.
      * @param fullCompare True to compare the full references as far as the range reaches.
      *
-    
-     * @return The result from zero to above. A negative number will be returned on error. */
+     * @return The result from zero to above. A negative number will be returned on error.
+     */
     public double getDifference(CommandParts other, boolean fullCompare) {
         // Make sure the other reference is correct
         if(other == null)
@@ -196,10 +195,10 @@ public class CommandParts {
     /**
      * Convert the parts to a string.
      *
-    
-     * @return The part as a string. */
+     * @return The part as a string.
+     */
     @Override
     public String toString() {
-        return ListUtils.implode(this.parts, " ");
+        return StringUtils.join(" ", this.parts);
     }
 }

src/main/java/fr/xephi/authme/command/help/HelpSyntaxHelper.java

@@ -1,13 +1,15 @@
 package fr.xephi.authme.command.help;
 
+import fr.xephi.authme.util.StringUtils;
 import org.bukkit.ChatColor;
 
 import fr.xephi.authme.command.CommandArgumentDescription;
 import fr.xephi.authme.command.CommandDescription;
 import fr.xephi.authme.command.CommandParts;
-import fr.xephi.authme.util.ListUtils;
 
 /**
+ * Helper class for formatting a command's structure (name and arguments)
+ * for a Minecraft user.
  */
 public final class HelpSyntaxHelper {
 
@@ -16,52 +18,63 @@ public final class HelpSyntaxHelper {
     }
 
     /**
-     * Get the proper syntax for a command.
+     * Get the formatted syntax for a command.
      *
-     * @param commandDescription The command to get the syntax for.
+     * @param commandDescription The command to build the syntax for.
      * @param commandReference The reference of the command.
      * @param alternativeLabel The alternative label to use for this command syntax.
      * @param highlight True to highlight the important parts of this command.
      *
      * @return The command with proper syntax.
      */
-    @SuppressWarnings("StringConcatenationInsideStringBufferAppend")
-    public static String getCommandSyntax(CommandDescription commandDescription, CommandParts commandReference, String alternativeLabel, boolean highlight) {
-        // Create a string builder to build the command
-        StringBuilder sb = new StringBuilder();
-
-        // Set the color and prefix a slash
-        sb.append(ChatColor.WHITE + "/");
+    public static String getCommandSyntax(CommandDescription commandDescription, CommandParts commandReference,
+                                          String alternativeLabel, boolean highlight) {
+        // Create a string builder with white color and prefixed slash
+        StringBuilder sb = new StringBuilder()
+            .append(ChatColor.WHITE)
+            .append("/");
 
         // Get the help command reference, and the command label
         CommandParts helpCommandReference = commandDescription.getCommandReference(commandReference);
-        final String parentCommand = (new CommandParts(helpCommandReference.getRange(0, helpCommandReference.getCount() - 1))).toString();
-        String commandLabel = helpCommandReference.get(helpCommandReference.getCount() - 1);
+        final String parentCommand = new CommandParts(
+                helpCommandReference.getRange(0, helpCommandReference.getCount() - 1)).toString();
 
         // Check whether the alternative label should be used
-        if (alternativeLabel != null && alternativeLabel.trim().length() > 0) {
+        String commandLabel;
+        if (StringUtils.isEmpty(alternativeLabel)) {
+            commandLabel = helpCommandReference.get(helpCommandReference.getCount() - 1);
+        } else {
             commandLabel = alternativeLabel;
         }
 
         // Show the important bit of the command, highlight this part if required
-        sb.append(ListUtils.implode(parentCommand, (highlight ? ChatColor.YELLOW + "" + ChatColor.BOLD : "") + commandLabel, " "));
-        if(highlight)
-            sb.append(ChatColor.YELLOW);
+        sb.append(parentCommand)
+            .append(" ")
+            .append(highlight ? ChatColor.YELLOW.toString() + ChatColor.BOLD : "")
+            .append(commandLabel);
 
-        // Add each command arguments
-        for(CommandArgumentDescription arg : commandDescription.getArguments()) {
-            // Add the argument as optional or non-optional argument
-            if(!arg.isOptional())
-                sb.append(ChatColor.ITALIC + " <" + arg.getLabel() + ">");
-            else
-                sb.append(ChatColor.ITALIC + " [" + arg.getLabel() + "]");
+        if (highlight) {
+            sb.append(ChatColor.YELLOW);
+        }
+
+        // Add each command argument
+        for (CommandArgumentDescription arg : commandDescription.getArguments()) {
+            sb.append(ChatColor.ITALIC).append(formatArgument(arg));
         }
 
         // Add some dots if the command allows unlimited arguments
-        if(commandDescription.getMaximumArguments() < 0)
-            sb.append(ChatColor.ITALIC + " ...");
+        if (commandDescription.getMaximumArguments() < 0) {
+            sb.append(ChatColor.ITALIC).append(" ...");
+        }
 
         // Return the build command syntax
         return sb.toString();
     }
+
+    private static String formatArgument(CommandArgumentDescription argument) {
+        if (argument.isOptional()) {
+            return " [" + argument.getLabel() + "]";
+        }
+        return " <" + argument.getLabel() + ">";
+    }
 }

src/main/java/fr/xephi/authme/util/ListUtils.java

@@ -1,58 +0,0 @@
-package fr.xephi.authme.util;
-
-import java.util.ArrayList;
-import java.util.List;
-
-/**
- */
-public class ListUtils {
-
-    /**
-     * Implode a list of elements into a single string, with a specified separator.
-     *
-     * @param elements The elements to implode.
-     * @param separator The separator to use.
-     *
-    
-     * @return The result string. */
-    public static String implode(List<String> elements, String separator) {
-        // Create a string builder
-        StringBuilder sb = new StringBuilder();
-
-        // Append each element
-        for(String element : elements) {
-            // Make sure the element isn't empty
-            if(element.trim().length() == 0)
-                continue;
-
-            // Prefix the separator if it isn't the first element
-            if(sb.length() > 0)
-                sb.append(separator);
-
-            // Append the element
-            sb.append(element);
-        }
-
-        // Return the result
-        return sb.toString();
-    }
-
-    /**
-     * Implode two elements into a single string, with a specified separator.
-     *
-     * @param element The first element to implode.
-     * @param otherElement The second element to implode.
-     * @param separator The separator to use.
-     *
-    
-     * @return The result string. */
-    public static String implode(String element, String otherElement, String separator) {
-        // Combine the lists
-        List<String> combined = new ArrayList<>();
-        combined.add(element);
-        combined.add(otherElement);
-
-        // Implode and return the result
-        return implode(combined, separator);
-    }
-}

src/main/java/fr/xephi/authme/util/StringUtils.java

@@ -5,17 +5,18 @@ import net.ricecode.similarity.StringSimilarityService;
 import net.ricecode.similarity.StringSimilarityServiceImpl;
 
 /**
+ * Utility class for String operations.
  */
 public class StringUtils {
 
     /**
      * Get the difference of two strings.
      *
-     * @param first First string.
-     * @param second Second string.
+     * @param first First string
+     * @param second Second string
      *
-    
-     * @return The difference value. */
+     * @return The difference value
+     */
     public static double getDifference(String first, String second) {
         // Make sure the strings are valid.
         if(first == null || second == null)
@@ -27,22 +28,60 @@ public class StringUtils {
         // Determine the difference value, return the result
         return Math.abs(service.score(first, second) - 1.0);
     }
-    
+
     /**
-     * Method containsAny.
-     * @param str String
-     * @param pieces String[]
-    
-     * @return boolean */
+     * Returns whether the given string contains any of the provided elements.
+     *
+     * @param str the string to analyze
+     * @param pieces the items to check the string for
+     *
+     * @return true if the string contains at least one of the items
+     */
     public static boolean containsAny(String str, String... pieces) {
     	if (str == null) {
     		return false;
     	}
     	for (String piece : pieces) {
-    		if (str.contains(piece)) {
+    		if (piece != null && str.contains(piece)) {
     			return true;
     		}
     	}
     	return false;
     }
+
+    /**
+     * Null-safe method for checking whether a string is empty. Note that the string
+     * is trimmed, so this method also considers a string with whitespace as empty.
+     *
+     * @param str the string to verify
+     *
+     * @return true if the string is empty, false otherwise
+     */
+    public static boolean isEmpty(String str) {
+        return str == null || str.trim().isEmpty();
+    }
+
+    /**
+     * Joins a list of elements into a single string with the specified delimiter.
+     *
+     * @param delimiter the delimiter to use
+     * @param elements the elements to join
+     *
+     * @return a new String that is composed of the elements separated by the delimiter
+     */
+    public static String join(String delimiter, Iterable<String> elements) {
+        StringBuilder sb = new StringBuilder();
+        for (String element : elements) {
+            if (!isEmpty(element)) {
+                // Add the separator if it isn't the first element
+                if (sb.length() > 0) {
+                    sb.append(delimiter);
+                }
+                sb.append(element);
+            }
+        }
+
+        return sb.toString();
+    }
+
 }

src/test/java/fr/xephi/authme/command/CommandPartsTest.java

@@ -0,0 +1,38 @@
+package fr.xephi.authme.command;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertThat;
+
+/**
+ * Test for {@link CommandParts}.
+ */
+public class CommandPartsTest {
+
+    @Test
+    public void shouldPrintPartsForStringRepresentation() {
+        // given
+        CommandParts parts = new CommandParts(Arrays.asList("some", "parts", "for", "test"));
+
+        // when
+        String str = parts.toString();
+
+        // then
+        assertThat(str, equalTo("some parts for test"));
+    }
+
+    @Test
+    public void shouldPrintEmptyStringForNoArguments() {
+        // given
+        CommandParts parts = new CommandParts();
+
+        // when
+        String str = parts.toString();
+
+        // then
+        assertThat(str, equalTo(""));
+    }
+}

src/test/java/fr/xephi/authme/util/StringUtilsTest.java

@@ -0,0 +1,87 @@
+package fr.xephi.authme.util;
+
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.hamcrest.Matchers.equalTo;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
+
+/**
+ * Test for {@link StringUtils}.
+ */
+public class StringUtilsTest {
+
+    @Test
+    public void shouldFindContainedItem() {
+        // given
+        String text = "This is a test of containsAny()";
+        String piece = "test";
+
+        // when
+        boolean result = StringUtils.containsAny(text, "some", "words", "that", "do not", "exist", piece);
+
+        // then
+        assertThat(result, equalTo(true));
+    }
+
+    @Test
+    public void shouldReturnFalseIfNoneFound() {
+        // given
+        String text = "This is a test string";
+
+        // when
+        boolean result = StringUtils.containsAny(text, "some", "other", "words", null);
+
+        // then
+        assertThat(result, equalTo(false));
+    }
+
+    @Test
+    public void shouldReturnFalseForNullString() {
+        // given/when
+        boolean result = StringUtils.containsAny(null, "some", "words", "to", "check");
+
+        // then
+        assertThat(result, equalTo(false));
+    }
+
+    @Test
+    public void shouldCheckIsEmptyUtil() {
+        // Should be true for null/empty/whitespace
+        assertTrue(StringUtils.isEmpty(null));
+        assertTrue(StringUtils.isEmpty(""));
+        assertTrue(StringUtils.isEmpty(" \t"));
+
+        // Should be false if string has content
+        assertFalse(StringUtils.isEmpty("P"));
+        assertFalse(StringUtils.isEmpty(" test"));
+    }
+
+    @Test
+    public void shouldJoinString() {
+        // given
+        List<String> elements = Arrays.asList("test", "for", null, "join", "StringUtils");
+
+        // when
+        String result = StringUtils.join(", ", elements);
+
+        // then
+        assertThat(result, equalTo("test, for, join, StringUtils"));
+    }
+
+    @Test
+    public void shouldNotHaveDelimiter() {
+        // given
+        List<String> elements = Arrays.asList(" ", null, "\t", "hello", null);
+
+        // when
+        String result = StringUtils.join("-", elements);
+
+        // then
+        assertThat(result, equalTo("hello"));
+    }
+}