JarCastingText Line Iterable
An easy way to iterate over all lines in a source of text while using memory proportional to the length of the longest line.
Installation
This is a Maven project with the following coordinates:
<dependency>
<groupId>us.bpsm</groupId>
<artifactId>text-line-iterable</artifactId>
<version>1.0.0</version>
</dependency>
It is available through the repositories Maven Central and OSS Sonatype Releases.
License
Text Line Iterator is relased under the Eclipse Public License - v 1.0.
Usage
@Test
public void usageExample() throws IOException {
final Charset utf8 = Charset.forName("UTF-8");
final Closer closer = Closer.create();
try {
// The file contains ten lines of the form:
// 1,one
// 2,two
// ...
// 10,ten
final TextLineIterable tlit =
closer.register(new TextLineIterable(someFile(), utf8));
// tlit is an Iterable: we can process lines using a for(:) loop
int numberOfCharacters = 0;
for (String line: tlit) {
numberOfCharacters += line.length();
}
assertEquals(60, numberOfCharacters);
// We can make use of FluentIterable's methods to do complex
// processing on our lines without ever needing to have them all
// in memory at once.
// We're going to gather a list of the names of even numbers
// whose names contain an odd number of characters.
final List<String> names;
names = tlit.transform(new Function<String,List<String>>() {
// split each line into value and name (list of two strings)
public List<String> apply(String s) {
return Arrays.asList(s.split(","));
}
}).filter(new Predicate<List<String>>() {
// select only those with even value and odd name length
public boolean apply(List<String> strings) {
int value = Integer.parseInt(strings.get(0));
String name = strings.get(1);
return value % 2 == 0 && name.length() % 2 != 0;
}
}).transform(new Function<List<String>,String>() {
// extract only the name from each (name, value) pair.
public String apply(List<String> strings) {
return strings.get(1);
}
}).toList();
assertEquals(Arrays.asList("two", "six", "eight", "ten"), names);
} catch (Throwable e) {
throw closer.rethrow(e);
} finally {
closer.close();
}
}
Dependencies
This code requires a recent version of Google Guava. The included pom.xml specifies version 17.0 though it may work with older versions as well.