In this code:
- We actually create the (temporary) file we want to read and delete it again at the end.
- Default charsets for reading text files are the work of the devil, we set UTF-8 explicitly.
- The files need to be properly closed with try-with-resources, this also applies to the stream approach.
- A “long” count as return value seems excessive, dropping to int.
package chapter11;
import org.junit.jupiter.api.AfterAll;
import org.junit.jupiter.api.BeforeAll;
import org.junit.jupiter.api.Test;
import java.io.*;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.stream.Stream;
import static org.junit.jupiter.api.Assertions.assertAll;
import static org.junit.jupiter.api.Assertions.assertEquals;
public class FileProcessingTest {
private static File actualFile;
private final static Charset charset = StandardCharsets.UTF_8;
// Creates a file "/tmp/WordCount13982583023783245787.java" for example
@BeforeAll
static void createTmpFile() throws IOException {
actualFile = File.createTempFile("WordCount", ".java");
try (FileWriter writer = new FileWriter(actualFile, charset)) {
writer.write("package foo;\n");
writer.write("public class X {\n");
writer.write("}\n");
writer.write("public class Y {\n");
writer.write("}\n");
}
}
@AfterAll
static void deleteTmpFile() throws IOException {
// or one could have installed a handler with deleteOnExit()
actualFile.delete();
}
interface WordCount {
int countInFile(String word, File file) throws IOException;
}
// https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/io/FileReader.html
// https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/io/BufferedReader.html
static class WordCountBefore implements WordCount {
public int countInFile(final String searchWord, final File file) throws IOException {
int count = 0;
// Use try-with-resources / automatic resource management to clean up.
// Specify the charset, "default chartset" is the devil's work!
try (final var bufferedReader = new BufferedReader(new FileReader(file, charset))) {
String line;
while ((line = bufferedReader.readLine()) != null) {
final String[] words = line.split(" ");
for (String word : words) {
if (word.equals(searchWord)) {
count++;
}
}
}
return count;
}
}
}
// https://docs.oracle.com/en/java/javase/18/docs/api/java.base/java/nio/file/Files.html
static class WordCountAfter implements WordCount {
// The Files.lines() call may throw IOException.
// Additionally, the count() this yields a "long", so we need to cast to fit the interface.
// We still must use try-with-resources to close the file.
public int countInFile(final String searchWord, final File file) throws IOException {
try (final Stream<String> stream = Files.lines(file.toPath(), charset)) {
return (int) stream
.flatMap(line -> Stream.of(line.split(" ")))
.filter(word -> word.equals(searchWord))
.count();
}
}
}
private static void commonFileProcessingTests(final WordCount wordCount, File file) {
assertAll(
() -> assertEquals(2, wordCount.countInFile("public", file)),
() -> assertEquals(1, wordCount.countInFile("package", file)));
}
@Test
void fileProcessingBefore() {
commonFileProcessingTests(new WordCountBefore(), actualFile);
}
@Test
void fileProcessingAfter() {
commonFileProcessingTests(new WordCountAfter(), actualFile);
}
}