java.io.FileJava

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# 定义

public class File implements Serializable, Comparable<File>传输和比较
private static final FileSystem fs = DefaultFileSystem.getFileSystem();设置为UnixFileSystem

# 原生函数

public native boolean checkAccess(File f, int access);检查文件操作权限
public native boolean createFileExclusively(String path) throws IOException;创建文件底层也是原生方法
public native boolean createDirectory(File f); 创建目录
删除逻辑：

    public boolean delete(File f) {
        // Keep canonicalization caches in sync after file deletion
        // and renaming operations. Could be more clever than this
        // (i.e., only remove/update affected entries) but probably
        // not worth it since these entries expire after 30 seconds
        // anyway.
        cache.clear();
        javaHomePrefixCache.clear();
        return delete0(f);
    }

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    // Caches for canonicalization results to improve startup performance.
    // The first cache handles repeated canonicalizations of the same path
    // name. The prefix cache handles repeated canonicalizations within the
    // same directory, and must not create results differing from the true
    // canonicalization algorithm in canonicalize_md.c. For this reason the
    // prefix cache is conservative and is not used for complex path names.
    private ExpiringCache cache = new ExpiringCache();
    // On Unix symlinks can jump anywhere in the file system, so we only
    // treat prefixes in java.home as trusted and cacheable in the
    // canonicalization algorithm
    private ExpiringCache javaHomePrefixCache = new ExpiringCache();

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    private native boolean delete0(File f); //原生删除方法

# 3. 内部类

TempDirectory类：

    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;
        }
    }

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PathStatus类的定义：


    /**
     * Enum type that indicates the status of a file path.
     */
    private static enum PathStatus { INVALID, CHECKED };

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