java-file-class demo code

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Thabo Ntsoko 2019-10-07 18:02:32 +02:00
parent 66f4d44c60
commit 76bcf49a7a
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package com.baeldung.file;
import org.junit.Test;
import java.io.*;
import java.util.Arrays;
import java.util.List;
import static org.junit.Assert.*;
public class FileClassDemoUnitTest {
@Test
public void givenDirectoryCreated_whenMkdirIsInvoked_thenDirectoryIsDeleted() {
File directory = new File("testDirectory");
if (!directory.isDirectory() || !directory.exists()) {
directory.mkdir();
}
assertTrue(directory.delete());
}
@Test
public void givenFileCreated_whenCreateNewFileIsInvoked_thenFileIsDeleted() throws IOException {
File file = new File("testFile.txt");
if (!file.isFile() || !file.exists()) {
file.createNewFile();
}
assertTrue(file.delete());
}
@Test
public void givenFileCreated_whenCreateNewFileInvoked_thenMetadataIsAsExpected() throws IOException {
// different Operating systems have different separator characters
String separatorCharacter = System.getProperty("file.separator");
File parentDirectory = makeDirectory("filesDirectory");
File childFile = new File(parentDirectory, "file1.txt");
childFile.createNewFile();
assertTrue(childFile.getName().equals("file1.txt"));
assertTrue(childFile.getParentFile().getName().equals(parentDirectory.getName()));
assertTrue(childFile.getPath().equals(parentDirectory.getPath() + separatorCharacter + "file1.txt"));
removeDirectory(parentDirectory);
}
@Test(expected = FileNotFoundException.class)
public void givenReadOnlyFileCreated_whenCreateNewFileInvoked_thenFileCannotBeWrittenTo() throws IOException {
File parentDirectory = makeDirectory("filesDirectory");
File childFile = new File(parentDirectory, "file1.txt");
childFile.createNewFile();
childFile.setWritable(false);
FileOutputStream fos = new FileOutputStream(childFile);
fos.write("Hello World".getBytes()); // write operation
fos.flush();
fos.close();
removeDirectory(parentDirectory);
}
@Test(expected = FileNotFoundException.class)
public void givenWriteOnlyFileCreated_whenCreateNewFileInvoked_thenFileCannotBeReadFrom() throws IOException {
File parentDirectory = makeDirectory("filesDirectory");
File childFile = new File(parentDirectory, "file1.txt");
childFile.createNewFile();
childFile.setReadable(false);
FileInputStream fis = new FileInputStream(childFile);
fis.read(); // read operation
fis.close();
removeDirectory(parentDirectory);
}
@Test
public void givenFilesCreatedInDirectory_whenCreateNewFileInvoked_thenTheyCanBeListedAsExpected() throws IOException {
File directory = makeDirectory("filtersDirectory");
File csvFile = new File(directory, "csvFile.csv");
csvFile.createNewFile();
File txtFile = new File(directory, "txtFile.txt");
txtFile.createNewFile();
//normal listing
assertEquals(2, directory.list().length);
//filtered listing
FilenameFilter csvFilter = (dir, ext) -> ext.endsWith(".csv");
assertEquals(1, directory.list(csvFilter).length);
removeDirectory(directory);
}
@Test
public void givenDirectoryIsCreated_whenMkdirInvoked_thenDirectoryCanBeRenamed() {
File source = makeDirectory("source");
File destination = makeDirectory("destination");
source.renameTo(destination);
assertFalse(source.isDirectory());
assertTrue(destination.isDirectory());
removeDirectory(destination);
}
@Test
public void givenDataIsWrittenToFile_whenWriteIsInvoked_thenFreeSpaceOnSystemDecreases() throws IOException {
String name = System.getProperty("user.home") + System.getProperty("file.separator") + "test";
File testDir = makeDirectory(name);
File sample = new File(testDir, "sample.txt");
long freeSpaceBeforeWrite = testDir.getFreeSpace();
writeSampleDataToFile(sample);
long freeSpaceAfterWrite = testDir.getFreeSpace();
assertTrue(freeSpaceAfterWrite < freeSpaceBeforeWrite);
removeDirectory(testDir);
}
private static File makeDirectory(String directoryName) {
File directory = new File(directoryName);
directory.mkdir();
if (directory.isDirectory()) {
return directory;
}
throw new RuntimeException("Directory not created for " + directoryName);
}
private static void removeDirectory(File directory) {
// make sure you don't delete your home directory here
if (directory.getPath().equals(System.getProperty("user.home"))) {
return;
}
// remove directory and its files from system
if (directory != null && directory.exists()) {
// delete all files inside the directory
File[] filesInDirectory = directory.listFiles();
if (filesInDirectory != null) {
List<File> files = Arrays.asList(filesInDirectory);
files.forEach(f -> deleteFile(f));
}
// finally delete the directory itself
deleteFile(directory);
}
}
private static void deleteFile(File fileToDelete) {
if (fileToDelete != null && fileToDelete.exists()) {
fileToDelete.delete();
}
}
private static void writeSampleDataToFile(File sample) throws IOException {
//write sample text to file
try (FileOutputStream out = new FileOutputStream(sample)) {
for (int i = 1; i <= 100000; i++) {
String sampleText = "Sample line number " + i + "\n";
out.write(sampleText.getBytes());
}
}
}
}