Java tutorial
/* * Copyright (c) 1998, 2016, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package java.io; import java.lang.annotation.Native; /** * Package-private abstract class for the local filesystem abstraction. */ abstract class FileSystem { /* -- Normalization and construction -- */ /** * Return the local filesystem's name-separator character. */ public abstract char getSeparator(); /** * Return the local filesystem's path-separator character. */ public abstract char getPathSeparator(); /** * Convert the given pathname string to normal form. If the string is * already in normal form then it is simply returned. */ public abstract String normalize(String path); /** * Compute the length of this pathname string's prefix. The pathname * string must be in normal form. */ public abstract int prefixLength(String path); /** * Resolve the child pathname string against the parent. * Both strings must be in normal form, and the result * will be in normal form. */ public abstract String resolve(String parent, String child); /** * Return the parent pathname string to be used when the parent-directory * argument in one of the two-argument File constructors is the empty * pathname. */ public abstract String getDefaultParent(); /** * Post-process the given URI path string if necessary. This is used on * win32, e.g., to transform "/c:/foo" into "c:/foo". The path string * still has slash separators; code in the File class will translate them * after this method returns. */ public abstract String fromURIPath(String path); /* -- Path operations -- */ /** * Tell whether or not the given abstract pathname is absolute. */ public abstract boolean isAbsolute(File f); /** * Resolve the given abstract pathname into absolute form. Invoked by the * getAbsolutePath and getCanonicalPath methods in the File class. */ public abstract String resolve(File f); public abstract String canonicalize(String path) throws IOException; /* -- Attribute accessors -- */ /* Constants for simple boolean attributes */ @Native public static final int BA_EXISTS = 0x01; @Native public static final int BA_REGULAR = 0x02; @Native public static final int BA_DIRECTORY = 0x04; @Native public static final int BA_HIDDEN = 0x08; /** * Return the simple boolean attributes for the file or directory denoted * by the given abstract pathname, or zero if it does not exist or some * other I/O error occurs. */ public abstract int getBooleanAttributes(File f); @Native public static final int ACCESS_READ = 0x04; @Native public static final int ACCESS_WRITE = 0x02; @Native public static final int ACCESS_EXECUTE = 0x01; /** * Check whether the file or directory denoted by the given abstract * pathname may be accessed by this process. The second argument specifies * which access, ACCESS_READ, ACCESS_WRITE or ACCESS_EXECUTE, to check. * Return false if access is denied or an I/O error occurs */ public abstract boolean checkAccess(File f, int access); /** * Set on or off the access permission (to owner only or to all) to the file * or directory denoted by the given abstract pathname, based on the parameters * enable, access and oweronly. */ public abstract boolean setPermission(File f, int access, boolean enable, boolean owneronly); /** * Return the time at which the file or directory denoted by the given * abstract pathname was last modified, or zero if it does not exist or * some other I/O error occurs. */ public abstract long getLastModifiedTime(File f); /** * Return the length in bytes of the file denoted by the given abstract * pathname, or zero if it does not exist, is a directory, or some other * I/O error occurs. */ public abstract long getLength(File f); /* -- File operations -- */ /** * Create a new empty file with the given pathname. Return * <code>true</code> if the file was created and <code>false</code> if a * file or directory with the given pathname already exists. Throw an * IOException if an I/O error occurs. */ public abstract boolean createFileExclusively(String pathname) throws IOException; /** * Delete the file or directory denoted by the given abstract pathname, * returning <code>true</code> if and only if the operation succeeds. */ public abstract boolean delete(File f); /** * List the elements of the directory denoted by the given abstract * pathname. Return an array of strings naming the elements of the * directory if successful; otherwise, return <code>null</code>. */ public abstract String[] list(File f); /** * Create a new directory denoted by the given abstract pathname, * returning <code>true</code> if and only if the operation succeeds. */ public abstract boolean createDirectory(File f); /** * Rename the file or directory denoted by the first abstract pathname to * the second abstract pathname, returning <code>true</code> if and only if * the operation succeeds. */ public abstract boolean rename(File f1, File f2); /** * Set the last-modified time of the file or directory denoted by the * given abstract pathname, returning <code>true</code> if and only if the * operation succeeds. */ public abstract boolean setLastModifiedTime(File f, long time); /** * Mark the file or directory denoted by the given abstract pathname as * read-only, returning <code>true</code> if and only if the operation * succeeds. */ public abstract boolean setReadOnly(File f); /* -- Filesystem interface -- */ /** * List the available filesystem roots. */ public abstract File[] listRoots(); /* -- Disk usage -- */ @Native public static final int SPACE_TOTAL = 0; @Native public static final int SPACE_FREE = 1; @Native public static final int SPACE_USABLE = 2; public abstract long getSpace(File f, int t); /* -- Basic infrastructure -- */ /** * Retrieve the maximum length of a component of a file path. * * @return The maximum length of a file path component. */ public abstract int getNameMax(String path); /** * Compare two abstract pathnames lexicographically. */ public abstract int compare(File f1, File f2); /** * Compute the hash code of an abstract pathname. */ public abstract int hashCode(File f); // Flags for enabling/disabling performance optimizations for file // name canonicalization static final boolean useCanonCaches; static final boolean useCanonPrefixCache; private static boolean getBooleanProperty(String prop, boolean defaultVal) { String value = System.getProperty(prop); return (value != null) ? Boolean.parseBoolean(value) : defaultVal; } static { useCanonCaches = getBooleanProperty("sun.io.useCanonCaches", false); useCanonPrefixCache = useCanonCaches && getBooleanProperty("sun.io.useCanonPrefixCache", false); } }