001/** 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017package org.apache.camel.util; 018 019import java.io.Closeable; 020import java.io.IOException; 021import java.util.Iterator; 022import java.util.concurrent.atomic.AtomicBoolean; 023 024import org.apache.camel.CamelContext; 025import org.apache.camel.Exchange; 026 027/** 028 * Skip based {@link Iterator} which skips the given {@link Iterator} a number of times. 029 */ 030public final class SkipIterator implements Iterator<Object>, Closeable { 031 032 private final CamelContext camelContext; 033 private final Exchange exchange; 034 private final Iterator<?> it; 035 private final int skip; 036 private boolean closed; 037 private final AtomicBoolean hasSkip = new AtomicBoolean(); 038 039 /** 040 * Creates a new skip iterator 041 * 042 * @param exchange the exchange used to create this group iterator 043 * @param it the iterator 044 * @param skip number of times to skip 045 * @throws IllegalArgumentException is thrown if skip is not a positive number 046 */ 047 public SkipIterator(Exchange exchange, Iterator<?> it, int skip) { 048 this.exchange = exchange; 049 this.camelContext = exchange.getContext(); 050 this.it = it; 051 this.skip = skip; 052 if (skip < 0) { 053 throw new IllegalArgumentException("Skip must not be a negative number, was: " + skip); 054 } 055 } 056 057 @Override 058 public void close() throws IOException { 059 try { 060 IOHelper.closeIterator(it); 061 } finally { 062 // we are now closed 063 closed = true; 064 } 065 } 066 067 @Override 068 public boolean hasNext() { 069 if (closed) { 070 return false; 071 } 072 073 if (hasSkip.compareAndSet(false, true)) { 074 doSkip(); 075 } 076 077 boolean answer = it.hasNext(); 078 if (!answer) { 079 // auto close 080 try { 081 close(); 082 } catch (IOException e) { 083 // ignore 084 } 085 } 086 return answer; 087 } 088 089 @Override 090 public Object next() { 091 if (hasSkip.compareAndSet(false, true)) { 092 doSkip(); 093 } 094 095 return it.next(); 096 } 097 098 private void doSkip() { 099 for (int i = 0; i < skip; i++) { 100 if (it.hasNext()) { 101 // skip 102 it.next(); 103 } 104 } 105 } 106 107 @Override 108 public void remove() { 109 it.remove(); 110 } 111}