File class common method
①, create a method
1.boolean createNewFile () returns true there is no return to the presence of false
2.boolean mkdir () to create the directory, if the parent directory does not exist, it will fail to create
3.boolean mkdirs () to create multi-level directory, if the parent directory does not exist will be created automatically
②, delete method
1.boolean delete () delete a file or directory, if indicates a directory, delete the directory must be empty before
2.boolean deleteOnExit () to delete files after completion
③, determination method
Whether 1.boolean canExecute () determines an executable file
2.boolean canRead () determines whether the file is readable
3.boolean canWrite () determines whether the file is writable
4.boolean exists () whether a file or directory exists
5.boolean isDirectory ( ) to determine whether this path is a directory
6.boolean isFile () to determine whether a file
7.boolean isHidden () to determine whether a hidden file
8.boolean isAbsolute () to determine whether the absolute path of the file does not exist can judge
④, acquisition method
1.String getName () Gets file or directory name this path represented
2.String getPath () Converts this path name for pathname string
3.String getAbsolutePath () Returns the absolute pathname of this abstract form
4.String getParent ( ) // If no parent returns null
5.long lastModified () // get the last modification time
6.long length () returns the length of the file denoted by this abstract pathname.
7.boolean renameTo (File f) Rename the file thus abstract pathname represented.
8.File [] liseRoots () // Get Machine letter
9.String [] list () Returns a string array, whereby a directory named abstract pathname in the file and directory.
10.String [] list (FilenameFilter filter) Returns a string array, the directory name thus satisfy the specified filter the files and directories of abstract pathname.
package java.io;
import java.net.URI;
import java.net.URL;
import java.net.MalformedURLException;
import java.net.URISyntaxException;
import java.util.List;
import java.util.ArrayList;
import java.security.AccessController;
import java.security.SecureRandom;
import java.nio.file.Path;
import java.nio.file.FileSystems;
import sun.security.action.GetPropertyAction;
public class File
implements Serializable, Comparable<File>
{
/**
* The FileSystem object representing the platform's local file system.
*/
private static final FileSystem fs = DefaultFileSystem.getFileSystem();
/**
* This abstract pathname's normalized pathname string. A normalized
* pathname string uses the default name-separator character and does not
* contain any duplicate or redundant separators.
*
* @serial
*/
private final String path;
/**
* Enum type that indicates the status of a file path.
*/
private static enum PathStatus { INVALID, CHECKED };
/**
* The flag indicating whether the file path is invalid.
*/
private transient PathStatus status = null;
final boolean isInvalid() {
if (status == null) {
status = (this.path.indexOf('\u0000') < 0) ? PathStatus.CHECKED
: PathStatus.INVALID;
}
return status == PathStatus.INVALID;
}
/**
* The length of this abstract pathname's prefix, or zero if it has no
* prefix.
*/
private final transient int prefixLength;
/**
* Returns the length of this abstract pathname's prefix.
* For use by FileSystem classes.
*/
int getPrefixLength() {
return prefixLength;
}
public static final char separatorChar = fs.getSeparator();
/**
* The system-dependent default name-separator character, represented as a
* string for convenience. This string contains a single character, namely
* <code>{@link #separatorChar}</code>.
*/
public static final String separator = "" + separatorChar;
public static final char pathSeparatorChar = fs.getPathSeparator();
public static final String pathSeparator = "" + pathSeparatorChar;
/* -- Constructors -- */
/**
* Internal constructor for already-normalized pathname strings.
*/
private File(String pathname, int prefixLength) {
this.path = pathname;
this.prefixLength = prefixLength;
}
/**
* Internal constructor for already-normalized pathname strings.
* The parameter order is used to disambiguate this method from the
* public(File, String) constructor.
*/
private File(String child, File parent) {
assert parent.path != null;
assert (!parent.path.equals(""));
this.path = fs.resolve(parent.path, child);
this.prefixLength = parent.prefixLength;
}
/**
* Creates a new <code>File</code> instance by converting the given
* pathname string into an abstract pathname. If the given string is
* the empty string, then the result is the empty abstract pathname.
*
* @param pathname A pathname string
* @throws NullPointerException
* If the <code>pathname</code> argument is <code>null</code>
*/
public File(String pathname) {
if (pathname == null) {
throw new NullPointerException();
}
this.path = fs.normalize(pathname);
this.prefixLength = fs.prefixLength(this.path);
}
public File(String parent, String child) {
if (child == null) {
throw new NullPointerException();
}
if (parent != null) {
if (parent.equals("")) {
this.path = fs.resolve(fs.getDefaultParent(),
fs.normalize(child));
} else {
this.path = fs.resolve(fs.normalize(parent),
fs.normalize(child));
}
} else {
this.path = fs.normalize(child);
}
this.prefixLength = fs.prefixLength(this.path);
}
public File(File parent, String child) {
if (child == null) {
throw new NullPointerException();
}
if (parent != null) {
if (parent.path.equals("")) {
this.path = fs.resolve(fs.getDefaultParent(),
fs.normalize(child));
} else {
this.path = fs.resolve(parent.path,
fs.normalize(child));
}
} else {
this.path = fs.normalize(child);
}
this.prefixLength = fs.prefixLength(this.path);
}
public File(URI uri) {
// Check our many preconditions
if (!uri.isAbsolute())
throw new IllegalArgumentException("URI is not absolute");
if (uri.isOpaque())
throw new IllegalArgumentException("URI is not hierarchical");
String scheme = uri.getScheme();
if ((scheme == null) || !scheme.equalsIgnoreCase("file"))
throw new IllegalArgumentException("URI scheme is not \"file\"");
if (uri.getAuthority() != null)
throw new IllegalArgumentException("URI has an authority component");
if (uri.getFragment() != null)
throw new IllegalArgumentException("URI has a fragment component");
if (uri.getQuery() != null)
throw new IllegalArgumentException("URI has a query component");
String p = uri.getPath();
if (p.equals(""))
throw new IllegalArgumentException("URI path component is empty");
// Okay, now initialize
p = fs.fromURIPath(p);
if (File.separatorChar != '/')
p = p.replace('/', File.separatorChar);
this.path = fs.normalize(p);
this.prefixLength = fs.prefixLength(this.path);
}
/* -- Path-component accessors -- */
/**
* Returns the name of the file or directory denoted by this abstract
* pathname. This is just the last name in the pathname's name
* sequence. If the pathname's name sequence is empty, then the empty
* string is returned.
*
* @return The name of the file or directory denoted by this abstract
* pathname, or the empty string if this pathname's name sequence
* is empty
*/
public String getName() {
int index = path.lastIndexOf(separatorChar);
if (index < prefixLength) return path.substring(prefixLength);
return path.substring(index + 1);
}
/**
* Returns the pathname string of this abstract pathname's parent, or
* <code>null</code> if this pathname does not name a parent directory.
*
* <p> The <em>parent</em> of an abstract pathname consists of the
* pathname's prefix, if any, and each name in the pathname's name
* sequence except for the last. If the name sequence is empty then
* the pathname does not name a parent directory.
*
* @return The pathname string of the parent directory named by this
* abstract pathname, or <code>null</code> if this pathname
* does not name a parent
*/
public String getParent() {
int index = path.lastIndexOf(separatorChar);
if (index < prefixLength) {
if ((prefixLength > 0) && (path.length() > prefixLength))
return path.substring(0, prefixLength);
return null;
}
return path.substring(0, index);
}
public File getParentFile() {
String p = this.getParent();
if (p == null) return null;
return new File(p, this.prefixLength);
}
/**
* Converts this abstract pathname into a pathname string. The resulting
* string uses the {@link #separator default name-separator character} to
* separate the names in the name sequence.
*
* @return The string form of this abstract pathname
*/
public String getPath() {
return path;
}
public boolean isAbsolute() {
return fs.isAbsolute(this);
}
public String getAbsolutePath() {
return fs.resolve(this);
}
public File getAbsoluteFile() {
String absPath = getAbsolutePath();
return new File(absPath, fs.prefixLength(absPath));
}
public String getCanonicalPath() throws IOException {
if (isInvalid()) {
throw new IOException("Invalid file path");
}
return fs.canonicalize(fs.resolve(this));
}
public File getCanonicalFile() throws IOException {
String canonPath = getCanonicalPath();
return new File(canonPath, fs.prefixLength(canonPath));
}
private static String slashify(String path, boolean isDirectory) {
String p = path;
if (File.separatorChar != '/')
p = p.replace(File.separatorChar, '/');
if (!p.startsWith("/"))
p = "/" + p;
if (!p.endsWith("/") && isDirectory)
p = p + "/";
return p;
}
@Deprecated
public URL toURL() throws MalformedURLException {
if (isInvalid()) {
throw new MalformedURLException("Invalid file path");
}
return new URL("file", "", slashify(getAbsolutePath(), isDirectory()));
}
public URI toURI() {
try {
File f = getAbsoluteFile();
String sp = slashify(f.getPath(), f.isDirectory());
if (sp.startsWith("//"))
sp = "//" + sp;
return new URI("file", null, sp, null);
} catch (URISyntaxException x) {
throw new Error(x); // Can't happen
}
}
public boolean canRead() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return false;
}
return fs.checkAccess(this, FileSystem.ACCESS_READ);
}
public boolean canWrite() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.checkAccess(this, FileSystem.ACCESS_WRITE);
}
public boolean exists() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return false;
}
return ((fs.getBooleanAttributes(this) & FileSystem.BA_EXISTS) != 0);
}
public boolean isDirectory() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return false;
}
return ((fs.getBooleanAttributes(this) & FileSystem.BA_DIRECTORY)
!= 0);
}
public boolean isFile() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return false;
}
return ((fs.getBooleanAttributes(this) & FileSystem.BA_REGULAR) != 0);
}
public boolean isHidden() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return false;
}
return ((fs.getBooleanAttributes(this) & FileSystem.BA_HIDDEN) != 0);
}
public long lastModified() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return 0L;
}
return fs.getLastModifiedTime(this);
}
public long length() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return 0L;
}
return fs.getLength(this);
}
/* -- File operations -- */
public boolean createNewFile() throws IOException {
SecurityManager security = System.getSecurityManager();
if (security != null) security.checkWrite(path);
if (isInvalid()) {
throw new IOException("Invalid file path");
}
return fs.createFileExclusively(path);
}
public boolean delete() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkDelete(path);
}
if (isInvalid()) {
return false;
}
return fs.delete(this);
}
public void deleteOnExit() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkDelete(path);
}
if (isInvalid()) {
return;
}
DeleteOnExitHook.add(path);
}
public String[] list() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkRead(path);
}
if (isInvalid()) {
return null;
}
return fs.list(this);
}
public String[] list(FilenameFilter filter) {
String names[] = list();
if ((names == null) || (filter == null)) {
return names;
}
List<String> v = new ArrayList<>();
for (int i = 0 ; i < names.length ; i++) {
if (filter.accept(this, names[i])) {
v.add(names[i]);
}
}
return v.toArray(new String[v.size()]);
}
public File[] listFiles() {
String[] ss = list();
if (ss == null) return null;
int n = ss.length;
File[] fs = new File[n];
for (int i = 0; i < n; i++) {
fs[i] = new File(ss[i], this);
}
return fs;
}
public File[] listFiles(FilenameFilter filter) {
String ss[] = list();
if (ss == null) return null;
ArrayList<File> files = new ArrayList<>();
for (String s : ss)
if ((filter == null) || filter.accept(this, s))
files.add(new File(s, this));
return files.toArray(new File[files.size()]);
}
/**
* Returns an array of abstract pathnames denoting the files and
* directories in the directory denoted by this abstract pathname that
* satisfy the specified filter. The behavior of this method is the same
* as that of the {@link #listFiles()} method, except that the pathnames in
* the returned array must satisfy the filter. If the given {@code filter}
* is {@code null} then all pathnames are accepted. Otherwise, a pathname
* satisfies the filter if and only if the value {@code true} results when
* the {@link FileFilter#accept FileFilter.accept(File)} method of the
* filter is invoked on the pathname.
*
* @param filter
* A file filter
*
* @return An array of abstract pathnames denoting the files and
* directories in the directory denoted by this abstract pathname.
* The array will be empty if the directory is empty. Returns
* {@code null} if this abstract pathname does not denote a
* directory, or if an I/O error occurs.
*
* @throws SecurityException
* If a security manager exists and its {@link
* SecurityManager#checkRead(String)} method denies read access to
* the directory
*
* @since 1.2
* @see java.nio.file.Files#newDirectoryStream(Path,java.nio.file.DirectoryStream.Filter)
*/
public File[] listFiles(FileFilter filter) {
String ss[] = list();
if (ss == null) return null;
ArrayList<File> files = new ArrayList<>();
for (String s : ss) {
File f = new File(s, this);
if ((filter == null) || filter.accept(f))
files.add(f);
}
return files.toArray(new File[files.size()]);
}
/**
* Creates the directory named by this abstract pathname.
*
* @return <code>true</code> if and only if the directory was
* created; <code>false</code> otherwise
*
* @throws SecurityException
* If a security manager exists and its <code>{@link
* java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
* method does not permit the named directory to be created
*/
public boolean mkdir() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.createDirectory(this);
}
/**
* Creates the directory named by this abstract pathname, including any
* necessary but nonexistent parent directories. Note that if this
* operation fails it may have succeeded in creating some of the necessary
* parent directories.
*
* @return <code>true</code> if and only if the directory was created,
* along with all necessary parent directories; <code>false</code>
* otherwise
*
* @throws SecurityException
* If a security manager exists and its <code>{@link
* java.lang.SecurityManager#checkRead(java.lang.String)}</code>
* method does not permit verification of the existence of the
* named directory and all necessary parent directories; or if
* the <code>{@link
* java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
* method does not permit the named directory and all necessary
* parent directories to be created
*/
public boolean mkdirs() {
if (exists()) {
return false;
}
if (mkdir()) {
return true;
}
File canonFile = null;
try {
canonFile = getCanonicalFile();
} catch (IOException e) {
return false;
}
File parent = canonFile.getParentFile();
return (parent != null && (parent.mkdirs() || parent.exists()) &&
canonFile.mkdir());
}
/**
* Renames the file denoted by this abstract pathname.
*
* <p> Many aspects of the behavior of this method are inherently
* platform-dependent: The rename operation might not be able to move a
* file from one filesystem to another, it might not be atomic, and it
* might not succeed if a file with the destination abstract pathname
* already exists. The return value should always be checked to make sure
* that the rename operation was successful.
*
* <p> Note that the {@link java.nio.file.Files} class defines the {@link
* java.nio.file.Files#move move} method to move or rename a file in a
* platform independent manner.
*
* @param dest The new abstract pathname for the named file
*
* @return <code>true</code> if and only if the renaming succeeded;
* <code>false</code> otherwise
*
* @throws SecurityException
* If a security manager exists and its <code>{@link
* java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
* method denies write access to either the old or new pathnames
*
* @throws NullPointerException
* If parameter <code>dest</code> is <code>null</code>
*/
public boolean renameTo(File dest) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
security.checkWrite(dest.path);
}
if (dest == null) {
throw new NullPointerException();
}
if (this.isInvalid() || dest.isInvalid()) {
return false;
}
return fs.rename(this, dest);
}
/**
* Sets the last-modified time of the file or directory named by this
* abstract pathname.
*
* <p> All platforms support file-modification times to the nearest second,
* but some provide more precision. The argument will be truncated to fit
* the supported precision. If the operation succeeds and no intervening
* operations on the file take place, then the next invocation of the
* <code>{@link #lastModified}</code> method will return the (possibly
* truncated) <code>time</code> argument that was passed to this method.
*
* @param time The new last-modified time, measured in milliseconds since
* the epoch (00:00:00 GMT, January 1, 1970)
*
* @return <code>true</code> if and only if the operation succeeded;
* <code>false</code> otherwise
*
* @throws IllegalArgumentException If the argument is negative
*
* @throws SecurityException
* If a security manager exists and its <code>{@link
* java.lang.SecurityManager#checkWrite(java.lang.String)}</code>
* method denies write access to the named file
*
* @since 1.2
*/
public boolean setLastModified(long time) {
if (time < 0) throw new IllegalArgumentException("Negative time");
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.setLastModifiedTime(this, time);
}
public boolean setReadOnly() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.setReadOnly(this);
}
public boolean setWritable(boolean writable, boolean ownerOnly) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.setPermission(this, FileSystem.ACCESS_WRITE, writable, ownerOnly);
}
public boolean setWritable(boolean writable) {
return setWritable(writable, true);
}
public boolean setReadable(boolean readable, boolean ownerOnly) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.setPermission(this, FileSystem.ACCESS_READ, readable, ownerOnly);
}
public boolean setReadable(boolean readable) {
return setReadable(readable, true);
}
public boolean setExecutable(boolean executable, boolean ownerOnly) {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkWrite(path);
}
if (isInvalid()) {
return false;
}
return fs.setPermission(this, FileSystem.ACCESS_EXECUTE, executable, ownerOnly);
}
public boolean setExecutable(boolean executable) {
return setExecutable(executable, true);
}
public boolean canExecute() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkExec(path);
}
if (isInvalid()) {
return false;
}
return fs.checkAccess(this, FileSystem.ACCESS_EXECUTE);
}
public static File[] listRoots() {
return fs.listRoots();
}
public long getTotalSpace() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
sm.checkRead(path);
}
if (isInvalid()) {
return 0L;
}
return fs.getSpace(this, FileSystem.SPACE_TOTAL);
}
public long getFreeSpace() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
sm.checkRead(path);
}
if (isInvalid()) {
return 0L;
}
return fs.getSpace(this, FileSystem.SPACE_FREE);
}
public long getUsableSpace() {
SecurityManager sm = System.getSecurityManager();
if (sm != null) {
sm.checkPermission(new RuntimePermission("getFileSystemAttributes"));
sm.checkRead(path);
}
if (isInvalid()) {
return 0L;
}
return fs.getSpace(this, FileSystem.SPACE_USABLE);
}
/* -- Temporary files -- */
private static class TempDirectory {
private TempDirectory() { }
// temporary directory location
private static final File tmpdir = new File(AccessController
.doPrivileged(new GetPropertyAction("java.io.tmpdir")));
static File location() {
return tmpdir;
}
// file name generation
private static final SecureRandom random = new SecureRandom();
static File generateFile(String prefix, String suffix, File dir)
throws IOException
{
long n = random.nextLong();
if (n == Long.MIN_VALUE) {
n = 0; // corner case
} else {
n = Math.abs(n);
}
// Use only the file name from the supplied prefix
prefix = (new File(prefix)).getName();
String name = prefix + Long.toString(n) + suffix;
File f = new File(dir, name);
if (!name.equals(f.getName()) || f.isInvalid()) {
if (System.getSecurityManager() != null)
throw new IOException("Unable to create temporary file");
else
throw new IOException("Unable to create temporary file, " + f);
}
return f;
}
}
public static File createTempFile(String prefix, String suffix,
File directory)
throws IOException
{
if (prefix.length() < 3)
throw new IllegalArgumentException("Prefix string too short");
if (suffix == null)
suffix = ".tmp";
File tmpdir = (directory != null) ? directory
: TempDirectory.location();
SecurityManager sm = System.getSecurityManager();
File f;
do {
f = TempDirectory.generateFile(prefix, suffix, tmpdir);
if (sm != null) {
try {
sm.checkWrite(f.getPath());
} catch (SecurityException se) {
// don't reveal temporary directory location
if (directory == null)
throw new SecurityException("Unable to create temporary file");
throw se;
}
}
} while ((fs.getBooleanAttributes(f) & FileSystem.BA_EXISTS) != 0);
if (!fs.createFileExclusively(f.getPath()))
throw new IOException("Unable to create temporary file");
return f;
}
public static File createTempFile(String prefix, String suffix)
throws IOException
{
return createTempFile(prefix, suffix, null);
}
public int compareTo(File pathname) {
return fs.compare(this, pathname);
}
public boolean equals(Object obj) {
if ((obj != null) && (obj instanceof File)) {
return compareTo((File)obj) == 0;
}
return false;
}
public int hashCode() {
return fs.hashCode(this);
}
public String toString() {
return getPath();
}
private synchronized void writeObject(java.io.ObjectOutputStream s)
throws IOException
{
s.defaultWriteObject();
s.writeChar(separatorChar); // Add the separator character
}
private synchronized void readObject(java.io.ObjectInputStream s)
throws IOException, ClassNotFoundException
{
ObjectInputStream.GetField fields = s.readFields();
String pathField = (String)fields.get("path", null);
char sep = s.readChar(); // read the previous separator char
if (sep != separatorChar)
pathField = pathField.replace(sep, separatorChar);
String path = fs.normalize(pathField);
UNSAFE.putObject(this, PATH_OFFSET, path);
UNSAFE.putIntVolatile(this, PREFIX_LENGTH_OFFSET, fs.prefixLength(path));
}
private static final long PATH_OFFSET;
private static final long PREFIX_LENGTH_OFFSET;
private static final sun.misc.Unsafe UNSAFE;
static {
try {
sun.misc.Unsafe unsafe = sun.misc.Unsafe.getUnsafe();
PATH_OFFSET = unsafe.objectFieldOffset(
File.class.getDeclaredField("path"));
PREFIX_LENGTH_OFFSET = unsafe.objectFieldOffset(
File.class.getDeclaredField("prefixLength"));
UNSAFE = unsafe;
} catch (ReflectiveOperationException e) {
throw new Error(e);
}
}
/** use serialVersionUID from JDK 1.0.2 for interoperability */
private static final long serialVersionUID = 301077366599181567L;
// -- Integration with java.nio.file --
private volatile transient Path filePath;
public Path toPath() {
Path result = filePath;
if (result == null) {
synchronized (this) {
result = filePath;
if (result == null) {
result = FileSystems.getDefault().getPath(path);
filePath = result;
}
}
}
return result;
}
}
