10File

野性酷女 2021-10-23 21:11 179阅读 0赞

File  
java.io.File类：文件和目录路径名的抽象表示形式  
通过File对象可以访问文件的属性。  
通过File对象创建空文件或目录（在该对象所指的文件或目录不存在的情况下）。  
File属性  
separator：系统文件路径分隔符  
public static final String separator = “” + separatorChar;  
separatorChar：  
public static final char separatorChar = fs.getSeparator();  
pathSeparator:  
public static final String pathSeparator = “” + pathSeparatorChar;  
pathSeparatorChar:  
public static final char pathSeparatorChar = fs.getPathSeparator();  
File构造函数  
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);
    }

File常用方法  
canRead()  
canWrite()  
canExecute()  
exists()  
isDirectory()  
isFile()  
isHidden()  
lastModified()  
length()  
getName()  
getPath() 如果是绝对路径，返回绝对路径，否则返回相对路径  
getAbsolutePath() 返回绝对路径  
getParent() 返回上一级目录，如果是相对，返回null  
通过File对象创建空文件或目录（在该对象所指的文件或目录不存在的情况下）  
createNewFile()  
delete()  
mkdir() 创建目录，父目录必须存在，否则失败  
mkdirs() 创建目录，父目录不存在一同创建  
作业：  
通过File获取指定路径下的文件夹及其子文件和文件夹。