fix IDE warnings

Author: mikesamuel

src/main/java/org/owasp/html/CssSchema.java

@@ -841,7 +841,8 @@ Property forKey(String propertyName) {
     DEFINITIONS = builder.build();
   }
 
-  private static <T> ImmutableSet<T> union(ImmutableSet<T>... subsets) {
+  private static <T> ImmutableSet<T> union(
+      @SuppressWarnings("unchecked") ImmutableSet<T>... subsets) {
     ImmutableSet.Builder<T> all = ImmutableSet.builder();
     for (ImmutableSet<T> subset : subsets) {
       all.addAll(subset);

src/main/java/org/owasp/html/Trie.java

@@ -78,7 +78,7 @@ private Trie(
       this.value = elements.get(pos).getValue();
       if (pos + 1 == end) {  // base case
         this.childMap = ZERO_CHARS;
-        this.children = ZERO_TRIES;
+        this.children = ((Trie<T>[]) ZERO_TRIES);
         return;
       } else {
         ++pos;
@@ -156,7 +156,7 @@ private static <U> List<Map.Entry<String, U>> sortedUniqEntries(
   }
 
   private static final char[] ZERO_CHARS = new char[0];
-  private static final Trie[] ZERO_TRIES = new Trie[0];
+  private static final Trie<?>[] ZERO_TRIES = new Trie<?>[0];
 
   /**
    * Append all strings s such that {@code this.lookup(s).isTerminal()} to the

src/test/java/org/owasp/html/SanitizersTest.java

@@ -453,11 +453,11 @@ private static class Permutations<T> implements Iterable<List<T>> {
     /** Permutation size. */
     final int k;
 
-    Permutations(T... elements) {
+    Permutations(@SuppressWarnings("unchecked") T... elements) {
       this(elements.length, elements);
     }
 
-    Permutations(int k, T... elements) {
+    Permutations(int k, @SuppressWarnings("unchecked") T... elements) {
       this.k = k;
       this.elements = ImmutableList.copyOf(elements);
     }