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.Scanner; 023import java.util.concurrent.atomic.AtomicBoolean; 024 025import org.apache.camel.CamelContext; 026import org.apache.camel.Exchange; 027 028/** 029 * Skip based {@link Iterator} which skips the given {@link Iterator} a number of times. 030 */ 031public final class SkipIterator implements Iterator<Object>, Closeable { 032 033 private final CamelContext camelContext; 034 private final Exchange exchange; 035 private final Iterator<?> it; 036 private final int skip; 037 private boolean closed; 038 private final AtomicBoolean hasSkip = new AtomicBoolean(); 039 040 /** 041 * Creates a new skip iterator 042 * 043 * @param exchange the exchange used to create this group iterator 044 * @param it the iterator 045 * @param skip number of times to skip 046 * @throws IllegalArgumentException is thrown if skip is not a positive number 047 */ 048 public SkipIterator(Exchange exchange, Iterator<?> it, int skip) { 049 this.exchange = exchange; 050 this.camelContext = exchange.getContext(); 051 this.it = it; 052 this.skip = skip; 053 if (skip < 0) { 054 throw new IllegalArgumentException("Skip must not be a negative number, was: " + skip); 055 } 056 } 057 058 @Override 059 public void close() throws IOException { 060 try { 061 if (it instanceof Scanner) { 062 // special for Scanner which implement the Closeable since JDK7 063 Scanner scanner = (Scanner) it; 064 scanner.close(); 065 IOException ioException = scanner.ioException(); 066 if (ioException != null) { 067 throw ioException; 068 } 069 } else if (it instanceof Closeable) { 070 IOHelper.closeWithException((Closeable) it); 071 } 072 } finally { 073 // we are now closed 074 closed = true; 075 } 076 } 077 078 @Override 079 public boolean hasNext() { 080 if (closed) { 081 return false; 082 } 083 084 if (hasSkip.compareAndSet(false, true)) { 085 doSkip(); 086 } 087 088 boolean answer = it.hasNext(); 089 if (!answer) { 090 // auto close 091 try { 092 close(); 093 } catch (IOException e) { 094 // ignore 095 } 096 } 097 return answer; 098 } 099 100 @Override 101 public Object next() { 102 if (hasSkip.compareAndSet(false, true)) { 103 doSkip(); 104 } 105 106 return it.next(); 107 } 108 109 private void doSkip() { 110 for (int i = 0; i < skip; i++) { 111 if (it.hasNext()) { 112 // skip 113 it.next(); 114 } 115 } 116 } 117 118 @Override 119 public void remove() { 120 it.remove(); 121 } 122}