package jetbrains.jetpad.base;

public abstract class BaseRegistration implements Registration {
  public static Registration empty() {
    return new BaseRegistration() {
      @Override
      protected void doRemove() {
      }
    };
  }

  private boolean myRemoved;

  protected abstract void doRemove();

  @Override
  public final void remove() {
    if (myRemoved) {
      throw new IllegalStateException();
    }
    doRemove();
    myRemoved = true;
  }
}

@@ -1,8 +1,610 @@
+/*%0A * Copyright 2012-2015 JetBrains s.r.o%0A *%0A * Licensed under the Apache License, Version 2.0 (the %22License%22);%0A * you may not use this file except in compliance with the License.%0A * You may obtain a copy of the License at%0A *%0A *   http://www.apache.org/licenses/LICENSE-2.0%0A *%0A * Unless required by applicable law or agreed to in writing, software%0A * distributed under the License is distributed on an %22AS IS%22 BASIS,%0A * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.%0A * See the License for the specific language governing permissions and%0A * limitations under the License.%0A */%0A
 package 

add liscence to BaseRegistration