com.landawn.abacus.util.LineIterator Maven / Gradle / Ivy
Show all versions of abacus-util-se Show documentation
/*
* 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 com.landawn.abacus.util;
import java.io.BufferedReader;
import java.io.Closeable;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.nio.charset.Charset;
import java.util.NoSuchElementException;
import com.landawn.abacus.exception.UncheckedIOException;
// TODO: Auto-generated Javadoc
/**
* Note: it's copied from Apache Commons IO developed at The Apache Software Foundation (http://www.apache.org/), or under the Apache License 2.0.
*
* An Iterator over the lines in a Reader.
*
* LineIterator holds a reference to an open Reader.
* 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 #closeAllQuietly(LineIterator)}
* method on the iterator.
*
* The recommended usage pattern is:
*
* try(LineIterator it = FileUtils.lineIterator(file, "UTF-8")) {
* while (it.hasNext()) {
* String line = it.nextLine();
* // do something with line
* }
* }
*
*
* @version $Id: LineIterator.java 1471767 2013-04-24 23:24:19Z sebb $
* @since 1.2
*/
public final class LineIterator extends ImmutableIterator implements Closeable {
// N.B. This class deliberately does not implement Iterable, see https://issues.apache.org/jira/browse/IO-181
/** 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;
/** The is closed. */
private boolean isClosed = false;
/**
* Constructs an iterator of the lines for a Reader.
*
* @param reader the Reader 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);
}
}
/**
* Returns an Iterator for the lines in a File using the default encoding for the VM.
*
* This method opens an InputStream for the file.
* When you have finished with the iterator you should close the stream
* to free internal resources. This can be done by calling the
* {@link LineIterator#close()} or
* {@link IOUtil#closeQuietly(LineIterator)} method.
*
* The recommended usage pattern is:
*
* LineIterator it = FileUtils.lineIterator(file, "UTF-8");
* try {
* while (it.hasNext()) {
* String line = it.nextLine();
* /// do something with line
* }
* } finally {
* closeQuietly(iterator);
* }
*
*
* If an exception occurs during the creation of the iterator, the
* underlying stream is closed.
*
file the file to open for input, must not be {@code null}
* @return an Iterator of the lines in the file, never {@code null}
* @throws UncheckedIOException in case of an I/O error (file closed)
* @see #lineIterator(File, Charset)
*/
public static LineIterator of(final File file) {
return of(file, Charsets.UTF_8);
}
/**
* Returns an Iterator for the lines in a File.
*
* This method opens an InputStream for the file.
* When you have finished with the iterator you should close the stream
* to free internal resources. This can be done by calling the
* {@link LineIterator#close()} or
* {@link IOUtil#closeQuietly(LineIterator)} method.
*
* The recommended usage pattern is:
*
* LineIterator it = FileUtils.lineIterator(file, "UTF-8");
* try {
* while (it.hasNext()) {
* String line = it.nextLine();
* /// do something with line
* }
* } finally {
* closeQuietly(iterator);
* }
*
*
* If an exception occurs during the creation of the iterator, the
* underlying stream is closed.
*
file the file to open for input, must not be {@code null}
encoding the encoding to use, {@code null} means platform default
* @return an Iterator of the lines in the file, never {@code null}
* @throws UncheckedIOException in case of an I/O error (file closed)
*/
public static LineIterator of(final File file, final Charset encoding) {
return IOUtil.iterate(file, encoding);
}
/**
*
* @param input
* @return
*/
public static LineIterator of(final InputStream input) {
return of(input, Charsets.UTF_8);
}
/**
* Returns an Iterator for the lines in an InputStream, using
* the character encoding specified (or default encoding if null).
*
* LineIterator holds a reference to the open
* InputStream specified here. When you have finished with
* the iterator you should close the stream to free internal resources.
* This can be done by closing the stream directly, or by calling
* {@link LineIterator#close()} or {@link IOUtil#closeQuietly(LineIterator)}.
*
* The recommended usage pattern is:
*
* try {
* LineIterator it = lineIterator(stream, charset);
* while (it.hasNext()) {
* String line = it.nextLine();
* /// do something with line
* }
* } finally {
* closeQuietly(stream);
* }
*
*
input the InputStream to read from, not null
encoding the encoding to use, null means platform default
* @return an Iterator of the lines in the reader, never null
* @throws IllegalArgumentException if the input is null
* @throws UncheckedIOException if an I/O error occurs, such as if the encoding is invalid
*/
public static LineIterator of(final InputStream input, final Charset encoding) {
return IOUtil.iterate(input, encoding);
}
/**
*
* @param reader
* @return
*/
public static LineIterator of(final Reader reader) {
return new LineIterator(reader);
}
// @SafeVarargs
// public static LineIterator[] of(final Reader... readers) {
// if (N.isNullOrEmpty(readers)) {
// return new LineIterator[0];
// }
//
// final LineIterator[] iterators = new LineIterator[readers.length];
//
// for (int i = 0, len = readers.length; i < len; i++) {
// iterators[i] = new LineIterator(readers[i]);
// }
//
// return iterators;
// }
// public static List of(final Collection readers) {
// if (N.isNullOrEmpty(readers)) {
// return new ArrayList<>();
// }
//
// final List iterators = new ArrayList<>(readers.size());
//
// for (Reader reader : readers) {
// iterators.add(new LineIterator(reader));
// }
//
// return iterators;
// }
//-----------------------------------------------------------------------
/**
* Indicates whether the Reader has more lines.
* If there is an IOException then {@link #close()} will
* be called on this instance.
*
* @return {@code true} if the Reader has more lines
* @throws IllegalStateException if an IO exception occurs
*/
@Override
public boolean hasNext() {
if (cachedLine != null) {
return true;
} else if (finished) {
return false;
} else {
try {
cachedLine = bufferedReader.readLine();
if (cachedLine == null) {
finished = true;
return false;
} else {
return true;
}
} catch (final IOException ioe) {
close();
throw new UncheckedIOException(ioe);
}
}
}
/**
* Returns the next line in the wrapped Reader.
*
* @return
* @throws NoSuchElementException if there is no line to return
*/
@Override
public String next() {
if (!hasNext()) {
throw new NoSuchElementException("No more lines");
}
final String res = cachedLine;
cachedLine = null;
return res;
}
/**
*
* @param
* @param action
* @throws E the e
*/
public void foreachRemaining(Throwables.Consumer action) throws E {
N.checkArgNotNull(action);
while (hasNext()) {
action.accept(next());
}
}
/**
* Closes the underlying Reader 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 Reader remains open.
* This method can safely be called multiple times.
*/
@Override
public void close() {
if (isClosed) {
return;
}
isClosed = true;
finished = true;
cachedLine = null;
IOUtil.closeQuietly(bufferedReader);
}
}