001 /* 002 * Copyright (c) 2007-2015 Concurrent, Inc. All Rights Reserved. 003 * 004 * Project and contact information: http://www.cascading.org/ 005 * 006 * This file is part of the Cascading project. 007 * 008 * Licensed under the Apache License, Version 2.0 (the "License"); 009 * you may not use this file except in compliance with the License. 010 * You may obtain a copy of the License at 011 * 012 * http://www.apache.org/licenses/LICENSE-2.0 013 * 014 * Unless required by applicable law or agreed to in writing, software 015 * distributed under the License is distributed on an "AS IS" BASIS, 016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 017 * See the License for the specific language governing permissions and 018 * limitations under the License. 019 */ 020 021 package cascading.operation; 022 023 import cascading.flow.FlowProcess; 024 import cascading.tuple.Fields; 025 import cascading.tuple.Tuple; 026 027 /** 028 * Class NoOp does nothing. It ignores all arguments and returns an empty {@link Tuple}, {@link Tuple#NULL}. 029 * <p/> 030 * Use with {@link Fields#SWAP} to retain unknown fields, or use the {@link cascading.pipe.assembly.Discard} 031 * sub-assembly. 032 * 033 * @see Insert 034 * @see cascading.pipe.assembly.Discard 035 */ 036 public class NoOp extends BaseOperation implements Function 037 { 038 /** Constructor NoOp creates a new NoOp instance that will ignore the argument values and return no output. */ 039 public NoOp() 040 { 041 super( ANY, Fields.NONE ); 042 } 043 044 @Override 045 public void operate( FlowProcess flowProcess, FunctionCall functionCall ) 046 { 047 functionCall.getOutputCollector().add( Tuple.NULL ); 048 } 049 }