org.dstadler.commons.io.BufferedReaderWithPeek Maven / Gradle / Ivy
Show all versions of commons-dost Show documentation
package org.dstadler.commons.io;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
/**
* A small wrapper around BufferedReader which supports a "peek"
* of the next line without actually removing it from the lines
* returned by "readLine()".
*
* The peeked line is still returned on the next readLine() call.
*
* This allows to look at the next line without removing it
* from the list of lines.
*/
public class BufferedReaderWithPeek implements AutoCloseable {
private final BufferedReader delegate;
private String peekedLine = null;
public BufferedReaderWithPeek(String file) throws FileNotFoundException {
this(new BufferedReader(new FileReader(file)));
}
public BufferedReaderWithPeek(BufferedReader delegate) {
this.delegate = delegate;
}
/**
* Return the next line without taking it off of the BufferedReader
*
* Calling this method multiple times without "readLine()" returns
* the same line.
*
* @return The line that would be returned by readLine(). Multiple calls will return the same line.
* Only calling readLine() will advance the reader.
* @throws java.io.IOException If reading from the reader fails
*/
public String peekLine() throws IOException {
if (peekedLine == null) {
peekedLine = delegate.readLine();
}
return peekedLine;
}
/**
* Returns the next line from the BufferedReader, not including any line-termination characters,
* may be the line that was previously returned via #peekLine().
* A String containing the contents of the line, or null if the end of the stream has been reached without reading any characters
*
* @return A String containing the contents of the line, not
* including any line-termination characters, or null if
* the end of the stream has been reached without reading
* any characters
*
* @exception IOException If an I/O error occurs
*
* @see java.io.BufferedReader#readLine() for details
*/
public String readLine() throws IOException {
if (peekedLine != null) {
String line = peekedLine;
peekedLine = null;
return line;
}
return delegate.readLine();
}
@Override
public void close() throws IOException {
delegate.close();
}
}