| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package org.apache.commons.io; |
| |
| import java.io.BufferedReader; |
| import java.io.IOException; |
| import java.io.Reader; |
| import java.util.Iterator; |
| import java.util.NoSuchElementException; |
| |
| /** |
| * An Iterator over the lines in a <code>Reader</code>. |
| * <p> |
| * <code>LineIterator</code> holds a reference to an open <code>Reader</code>. |
| * When you have finished with the iterator you should close the reader |
| * to free internal resources. This can be done by closing the reader directly, |
| * or by calling the {@link #close()} or {@link #closeQuietly(LineIterator)} |
| * method on the iterator. |
| * <p> |
| * The recommended usage pattern is: |
| * <pre> |
| * LineIterator it = FileUtils.lineIterator(file, "UTF-8"); |
| * try { |
| * while (it.hasNext()) { |
| * String line = it.nextLine(); |
| * /// do something with line |
| * } |
| * } finally { |
| * LineIterator.closeQuietly(iterator); |
| * } |
| * </pre> |
| * |
| * @author Niall Pemberton |
| * @author Stephen Colebourne |
| * @author Sandy McArthur |
| * @version $Id: LineIterator.java 437567 2006-08-28 06:39:07Z bayard $ |
| * @since Commons IO 1.2 |
| */ |
| public class LineIterator implements Iterator { |
| |
| /** The reader that is being read. */ |
| private final BufferedReader bufferedReader; |
| /** The current line. */ |
| private String cachedLine; |
| /** A flag indicating if the iterator has been fully read. */ |
| private boolean finished = false; |
| |
| /** |
| * Constructs an iterator of the lines for a <code>Reader</code>. |
| * |
| * @param reader the <code>Reader</code> to read from, not null |
| * @throws IllegalArgumentException if the reader is null |
| */ |
| public LineIterator(final Reader reader) throws IllegalArgumentException { |
| if (reader == null) { |
| throw new IllegalArgumentException("Reader must not be null"); |
| } |
| if (reader instanceof BufferedReader) { |
| bufferedReader = (BufferedReader) reader; |
| } else { |
| bufferedReader = new BufferedReader(reader); |
| } |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Indicates whether the <code>Reader</code> has more lines. |
| * If there is an <code>IOException</code> then {@link #close()} will |
| * be called on this instance. |
| * |
| * @return <code>true</code> if the Reader has more lines |
| * @throws IllegalStateException if an IO exception occurs |
| */ |
| public boolean hasNext() { |
| if (cachedLine != null) { |
| return true; |
| } else if (finished) { |
| return false; |
| } else { |
| try { |
| while (true) { |
| String line = bufferedReader.readLine(); |
| if (line == null) { |
| finished = true; |
| return false; |
| } else if (isValidLine(line)) { |
| cachedLine = line; |
| return true; |
| } |
| } |
| } catch(IOException ioe) { |
| close(); |
| throw new IllegalStateException(ioe.toString()); |
| } |
| } |
| } |
| |
| /** |
| * Overridable method to validate each line that is returned. |
| * |
| * @param line the line that is to be validated |
| * @return true if valid, false to remove from the iterator |
| */ |
| protected boolean isValidLine(String line) { |
| return true; |
| } |
| |
| /** |
| * Returns the next line in the wrapped <code>Reader</code>. |
| * |
| * @return the next line from the input |
| * @throws NoSuchElementException if there is no line to return |
| */ |
| public Object next() { |
| return nextLine(); |
| } |
| |
| /** |
| * Returns the next line in the wrapped <code>Reader</code>. |
| * |
| * @return the next line from the input |
| * @throws NoSuchElementException if there is no line to return |
| */ |
| public String nextLine() { |
| if (!hasNext()) { |
| throw new NoSuchElementException("No more lines"); |
| } |
| String currentLine = cachedLine; |
| cachedLine = null; |
| return currentLine; |
| } |
| |
| /** |
| * Closes the underlying <code>Reader</code> quietly. |
| * This method is useful if you only want to process the first few |
| * lines of a larger file. If you do not close the iterator |
| * then the <code>Reader</code> remains open. |
| * This method can safely be called multiple times. |
| */ |
| public void close() { |
| finished = true; |
| IOUtils.closeQuietly(bufferedReader); |
| cachedLine = null; |
| } |
| |
| /** |
| * Unsupported. |
| * |
| * @throws UnsupportedOperationException always |
| */ |
| public void remove() { |
| throw new UnsupportedOperationException("Remove unsupported on LineIterator"); |
| } |
| |
| //----------------------------------------------------------------------- |
| /** |
| * Closes the iterator, handling null and ignoring exceptions. |
| * |
| * @param iterator the iterator to close |
| */ |
| public static void closeQuietly(LineIterator iterator) { |
| if (iterator != null) { |
| iterator.close(); |
| } |
| } |
| |
| } |