KeywordEnum: replace more String Keywords checks with Enums

forge-core/src/main/java/forge/util/Visitor.java

@@ -1,11 +1,22 @@
 package forge.util;
 
 public abstract class Visitor<T> {
+    /**
+     * visit the object
+     * the Visitor should return true it can be visit again
+     * returning false means the outer function can stop
+     *
+     * @param object
+     * @return boolean
+     */
     public abstract boolean visit(T object);
 
-    public void visitAll(Iterable<? extends T> objects) {
+    public boolean visitAll(Iterable<? extends T> objects) {
         for (T obj : objects) {
-            visit(obj);
+            if (!visit(obj)) {
+                return false;
+            }
         }
+        return true;
     }
 }