io.cdap.wrangler.service.explorer

Class BoundedLineInputStream

java.lang.Object

io.cdap.wrangler.service.explorer.BoundedLineInputStream

All Implemented Interfaces:

Closeable, AutoCloseable, Iterator<String>

public final class BoundedLineInputStream
extends Object
implements Iterator<String>, Closeable

This class provides an wrapper over the InputStream that limits the number of lines being read from the file. Uses a BufferedReader internally to read the data. If the number of lines in file is fewer than the lines in file, it will return only the lines that can be possibly read.

Constructor Summary

Constructors

Constructor and Description
BoundedLineInputStream(Reader reader, int lines) Constructs an iterator of the lines for a Reader.

Method Summary

Modifier and Type	Method and Description
void	close() Closes the underlying Reader quietly.
static void	closeQuietly(BoundedLineInputStream iterator) Closes the iterator, handling null and ignoring exceptions.
boolean	hasNext() Indicates whether the Reader has more lines.
protected boolean	isValidLine(String line) Overridable method to validate each line that is returned.
static BoundedLineInputStream	iterator(InputStream input, Charset encoding, int lines) A static method to create instance of BoundedLineInputStream.
static BoundedLineInputStream	iterator(InputStream input, String encoding, int lines)
String	next() Returns the next line in the wrapped Reader.
String	nextLine() Returns the next line in the wrapped Reader.
void	remove() Unsupported.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface java.util.Iterator

forEachRemaining

Constructor Detail

BoundedLineInputStream

public BoundedLineInputStream(Reader reader,
                              int lines)
                       throws IllegalArgumentException

Constructs an iterator of the lines for a Reader.

Parameters:

reader - the Reader to read from, not null

Throws:

IllegalArgumentException - if the reader is null

Method Detail

hasNext

public boolean hasNext()

Indicates whether the Reader has more lines. If there is an IOException then close() will be called on this instance.

Specified by:

hasNext in interface Iterator<String>

Returns:

true if the Reader has more lines

Throws:

IllegalStateException - if an IO exception occurs

isValidLine

protected boolean isValidLine(String line)

Overridable method to validate each line that is returned.

Parameters:

line - the line that is to be validated

Returns:

true if valid, false to remove from the iterator

next

public String next()

Returns the next line in the wrapped Reader.

Specified by:

next in interface Iterator<String>

Returns:

the next line from the input

Throws:

NoSuchElementException - if there is no line to return

nextLine

public String nextLine()

Returns the next line in the wrapped Reader.

Returns:

the next line from the input

Throws:

NoSuchElementException - if there is no line to return

close

public void close()

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.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

remove

public void remove()

Unsupported.

Specified by:

remove in interface Iterator<String>

Throws:

UnsupportedOperationException - always

closeQuietly

public static void closeQuietly(BoundedLineInputStream iterator)

Closes the iterator, handling null and ignoring exceptions.

Parameters:

iterator - the iterator to close

iterator

public static BoundedLineInputStream iterator(InputStream input,
                                              Charset encoding,
                                              int lines)
                                       throws IOException

A static method to create instance of BoundedLineInputStream. This method creates the instance specifying the character encoding and number of lines to be read.

The application using this method should ensure that they call BoundedLineInputStream.close() once the application has finished reading. When 'lines' is greater than number of the files in the file, it will be terminated once the end of the file is reached.

Parameters:

input - Input stream.

encoding - Type of encoding for the file.

lines - number of lines to be read.

Returns:

Iterator.

Throws:

IOException

iterator

public static BoundedLineInputStream iterator(InputStream input,
                                              String encoding,
                                              int lines)
                                       throws IOException

Throws:

IOException