Guava IO

Maven Dependency

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>org.fool.guava</groupId>
	<artifactId>guava</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>jar</packaging>

	<name>guava</name>
	<url>http://maven.apache.org</url>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
	</properties>

	<dependencies>
		<dependency>
			<groupId>com.google.guava</groupId>
			<artifactId>guava</artifactId>
			<version>19.0</version>
		</dependency>

		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.12</version>
		</dependency>
	</dependencies>

</project>

 

Copy

@Test
public void testCopy() throws IOException {
	File original = new File("src/main/resources/original.txt");
	File copy = new File("src/main/resources/copy.txt");

	Files.copy(original, copy);
}

 

Move

@Test
public void testMove() throws IOException {
	File copy = new File("src/main/resources/copy.txt");
	File newFile = new File("src/main/resources/newFile.txt");

	Files.move(copy, newFile);
}

 

Hash

@Test
public void testHashFile() throws IOException {
	File file = new File("src/main/resources/hash.txt");

	HashCode hashCode = Files.hash(file, Hashing.md5());

	System.out.println(hashCode);
}

 

Write

@Test
public void testWrite() throws IOException {
	File file = new File("src/main/resources/lines.txt");

	Files.write("LiuBei\nGuanYu\nZhangFei", file, Charsets.UTF_8);

	String result = Files.toString(file, Charsets.UTF_8);
	String expectedValue = "LiuBei\nGuanYu\nZhangFei";

	assertThat(result, equalTo(expectedValue));
}

 

ReadLines

@Test
public void testReadLines() throws IOException {
	File file = new File("src/main/resources/lines.txt");

	List<String> expectedLines = Lists.newArrayList("LiuBei", "GuanYu", "ZhangFei");

	List<String> readLines = Files.readLines(file, Charsets.UTF_8);

	assertThat(readLines, equalTo(expectedLines));
}

 

ReadLinesWithProcessor

@Test
public void testReadLinesWithProcessor() throws IOException {
	File file = new File("src/main/resources/books.txt");

	List<String> expectedLines = Lists.newArrayList("SanGuoYanYi", "ShuiHuZhuan", "XiYouJi", "HongLouMeng");

	List<String> readLines = Files.readLines(file, Charsets.UTF_8, new LineProcessor<List<String>>() {

		private List<String> bookTitles = Lists.newArrayList();

		@Override
		public boolean processLine(String line) throws IOException {
			bookTitles.add(Iterables.get(Splitter.on(",").split(line), 1));
			return true;
		}

		@Override
		public List<String> getResult() {
			return bookTitles;
		}
	});

	assertThat(readLines, equalTo(expectedLines));
}

 

Append

@Test
public void testAppendingWritingToFile() throws IOException {
	File file = new File("src/main/resources/quote.txt");
	file.deleteOnExit();

	String hamletQuoteStart = "To be, or not to be";

	Files.write(hamletQuoteStart, file, Charsets.UTF_8);

	assertThat(Files.toString(file, Charsets.UTF_8), equalTo(hamletQuoteStart));

	String hamletQuoteEnd = ", that is the question";

	Files.append(hamletQuoteEnd, file, Charsets.UTF_8);

	assertThat(Files.toString(file, Charsets.UTF_8), equalTo(hamletQuoteStart + hamletQuoteEnd));

	String overwrite = "Overwriting the file";

	Files.write(overwrite, file, Charsets.UTF_8);

	assertThat(Files.toString(file, Charsets.UTF_8), equalTo(overwrite));
}

 

ByteSink

@Test
public void testByteSink() throws IOException {
	String expectedValue = "Hello World";

	File file = new File("src/main/resources/helloworld.txt");

	ByteSink byteSink = Files.asByteSink(file);

	byteSink.write("Hello World".getBytes());

	String result = Files.toString(file, Charsets.UTF_8);

	assertThat(result, equalTo(expectedValue));
}

 

ByteSource

@Test
public void testByteSource() throws IOException {
	File file = new File("src/main/resources/helloworld.txt");

	ByteSource byteSource = Files.asByteSource(file);

	byte[] result = byteSource.read();

	assertThat(result, equalTo(Files.toByteArray(file)));

	System.out.println(new String(result));

	String expectedResult = "lo World";
	long offset = 3;
	long len = 1000;

	ByteSource sliceSource = Files.asByteSource(file).slice(offset, len);

	result = sliceSource.read();

	assertEquals(expectedResult, new String(result));

	System.out.println(new String(result));
}

 

CharSink

@Test
public void testCharSink() throws IOException {
	String expectedValue = "Hello World";

	File file = new File("src/main/resources/helloworld.txt");

	CharSink charSink = Files.asCharSink(file, Charsets.UTF_8);
	charSink.write("Hello World");

	String result = Files.toString(file, Charsets.UTF_8);

	System.out.println(result);

	assertThat(result, equalTo(expectedValue));
}

 

CharSource

@Test
public void testCharSource() throws IOException {
	String expectedValue = "Hello World";

	File file = new File("src/main/resources/helloworld.txt");

	CharSource charSource = Files.asCharSource(file, Charsets.UTF_8);

	String result = charSource.read();

	System.out.println(result);

	assertThat(result, equalTo(expectedValue));
}

 

ByteStreams

@Test
public void testByteStreams() throws IOException {
	Closer closer = Closer.create();

	BufferedInputStream in = new BufferedInputStream(
			new FileInputStream(new File("src/main/resources/helloworld.txt")));

	closer.register(in);

	byte[] result = ByteStreams.toByteArray(in);

	closer.close();

	String expectedValue = "Hello World";

	assertThat(new String(result), equalTo(expectedValue));

	System.out.println(new String(result));
}

 

CharStreams

@Test
public void testCharStreams() throws IOException {
	Closer closer = Closer.create();

	BufferedReader reader = new BufferedReader(new FileReader(new File("src/main/resources/helloworld.txt")));

	closer.register(reader);

	String result = CharStreams.toString(reader);
	
	closer.close();

	String expectedValue = "Hello World";

	assertThat(new String(result), equalTo(expectedValue));
	
	System.out.println(result);
}

 

Closer

package org.fool.guava.io;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;

import com.google.common.io.Closer;

public class CloserTest {
	public static void main(String[] args) throws IOException {
		Closer closer = Closer.create();
		
		try {
			BufferedReader reader = new BufferedReader(new FileReader(new File("src/main/resources/reader.txt")));
			BufferedWriter writer = new BufferedWriter(new FileWriter(new File("src/main/resources/writer.txt")));
			
			closer.register(reader);
			closer.register(writer);
			
			String line;
			while ((line = reader.readLine()) != null) {
				writer.write(line);
			}
		} catch (Throwable t) {
			throw closer.rethrow(t);
		} finally {
			closer.close();
		}
	}
}