Revert "Made getRequiredTokens and getAcceptableTokens as abstract, issue #655" as we will do that in 7.0 version

This reverts commit efac6bf023.

src/main/java/com/puppycrawl/tools/checkstyle/api/Check.java

@@ -22,6 +22,8 @@ package com.puppycrawl.tools.checkstyle.api;
 import java.util.Collections;
 import java.util.Set;
 
+import org.apache.commons.lang3.ArrayUtils;
+
 import com.google.common.collect.Sets;
 import com.puppycrawl.tools.checkstyle.Utils;
 
@@ -70,17 +72,25 @@ public abstract class Check extends AbstractViolationReporter {
      * The configurable token set.
      * Used to protect Checks against malicious users who specify an
      * unacceptable token set in the configuration file.
+     * The default implementation returns the check's default tokens.
      * @return the token set this check is designed for.
      * @see TokenTypes
      */
-    public abstract int[] getAcceptableTokens();
+    public int[] getAcceptableTokens() {
+        final int[] defaultTokens = getDefaultTokens();
+        final int[] copy = new int[defaultTokens.length];
+        System.arraycopy(defaultTokens, 0, copy, 0, defaultTokens.length);
+        return copy;
+    }
 
     /**
      * The tokens that this check must be registered for.
      * @return the token set this must be registered for.
      * @see TokenTypes
      */
-    public abstract int[] getRequiredTokens();
+    public int[] getRequiredTokens() {
+        return ArrayUtils.EMPTY_INT_ARRAY;
+    }
 
     /**
      * Adds a set of tokens the check is interested in.

src/test/java/com/puppycrawl/tools/checkstyle/api/CheckTest.java

@@ -20,10 +20,45 @@
 package com.puppycrawl.tools.checkstyle.api;
 
 import org.apache.commons.lang3.ArrayUtils;
+import org.junit.Assert;
 import org.junit.Test;
 
 public class CheckTest {
 
+    @Test
+    public void testGetRequiredTokens() {
+        Check check = new Check() {
+            @Override
+            public int[] getDefaultTokens() {
+                return ArrayUtils.EMPTY_INT_ARRAY;
+            }
+
+            @Override
+            public int[] getRequiredTokens() {
+                return super.getRequiredTokens();
+            }
+        };
+        // Eventually it will become clear abstract method
+        Assert.assertArrayEquals(ArrayUtils.EMPTY_INT_ARRAY, check.getRequiredTokens());
+    }
+
+    @Test
+    public void testGetAcceptable() {
+        Check check = new Check() {
+            @Override
+            public int[] getDefaultTokens() {
+                return ArrayUtils.EMPTY_INT_ARRAY;
+            }
+
+            @Override
+            public int[] getAcceptableTokens() {
+                return super.getAcceptableTokens();
+            }
+        };
+        // Eventually it will become clear abstract method
+        Assert.assertArrayEquals(ArrayUtils.EMPTY_INT_ARRAY, check.getAcceptableTokens());
+    }
+
     @Test
     public void testVisitToken() {
         Check check = new Check() {