流与文件（Java核心技术卷Ⅱ）

byte[] bytes=buffer.array();

byte[] bytes=...

ByteBuffer bbuf=ByteBuffer.wrap(bytes,offset,length);

CharBuffer cbuf=cset.decode(bbuf);

String str=cbuf.toString();

1.3 读写二进制数据

RandomAccessFile inOut=new RandomAccessFile("data.dat","rw");

long n=3;

in.seek((n-1)*RECORD_SIZE);

Employee e=new Employee();

e.readData(in);

1.4 ZIP文档

/* 通读ZIP文件 */
ZipInputStream zin=new ZipInputStream(new FileInputStream("ziptest.zip"));
ZipEntry entry;
while((entry=zin.getNextEntry())!=null){
do something
zin.closeEntry();
}
zin.close();

Scanner in=new Scanner(zin);

while(in.hasNextLine())

do something with in.nextLine()

/* 写出到ZIP文件 */
FileOutputStream fout=new FileOutputStream("test.zip");
ZipOutputStream zout=new ZipOutputStream(fout);
for all files{
ZipEntry ze=new ZipEntry(filename);
zout.putNextEntry(ze);
send data to zout
zout.closeEntry();
}
zout.close();

1.5 对象流与序列化

ObjectOutputStream out= new ObjectOutputStream(new FileOutputStream("employee.dat"));

Employee harry=new Employee("Harry Hacker",50000);

out.writeObject(harry);

ObjectInputStream in=new ObjectInputStream(new FileInputStream("employee.dat"));

74 两字节表示的字符串长度 所有字符

74 00 05 harry

72 2字节的类名长度 类名 8字节长的指纹 1字节长的标志 2字节长的数据域描述符的数量 数据域描述符 78（结束标记） 超类类型（如果没有就是70）

1字节长的类型编码 2字节长的域名长度 域名 类名（如果域是对象）

D 00 06 salary

75 类描述符 4字节长的数组项的数量 数组项

00 7E 00 00

71 00 7E 00 00

70

private void readObject(ObjectInputStream in) throws IOException,ClassNotFoundException;

private void writeObject(ObjectOutputStream out) throws IOException;

protected Object readResolve() throws ObjectStreamException{
if(value==1) return ...
if(value==2) return ..
return null;//一般情况下不应该发生
}

serialver Employee

public static final long serialVersionUID=.....;

1.6 操作文件

Path workPath=basePath.resolve("work");

/opt/myapp/work

Path tempPath=workPath.resolveSibling("temp");

/opt/myapp/temp

byte[] bytes=Files.readAllBytes(path);

String content=new String(bytes,charset);

List<String> lines=Files.readAllLines(path,charset);

Files.write(path,content.getBytes(charset));

Files.write(path,content.getBytes(charset),StandardOpenOption.APPEND);

Files.write(path,lines);

Files.copy(fromPath,toPath);

Files.move(fromPath,toPath);

Files.copy(fromPath,toPath,StandardCopyOption.REPLACE_EXISTING,StandardCopyOption.COPY_ATTRIBUTES);

Files.move(fromPath,toPath,StandardCopyOption.ATOMIC_MOVE);

Files.delete(path);

boolean deleted=Files.deleteIfExists(path);

Files.createDirectory(path);

Files.createDirectories(path);

Files.createFile(path);

long fileSize=Files.size(path);

BasicFileAttributes attributes=files.readAttributes(path,BasicFileAttribtutes.class);

try(DirectoryStream<Path> entries=Files.newDirectoryStream(dir)){
for(Path entry: entries)
process entries
}

DirectoryStream<Path> entries=Files.newDirectoryStream(dir,"*.java");

FileSystem fs=FileSystems.newFileSystem(Paths.get("D:\\workspace\\ziptest.zip"), null);

Files.copy(fs.getPath(sourceName), targetPath);

1.7 内存映射文件

FileChannel channel=FileChannel.open(path,options);

while(buffer.hasRemaining){ byte b=buffer.get();}

for(int i=0;i>buffer.limit();i++){byte b=buffer.get(i);}

ByteBuffer buffer=ByteBuffer.allocate(RECORD_SIZE);
channel.read(buffer);
channel.position(newpos);
buffer.flip();
channel.write(buffer);

FileChannel channel=FileChannel.open(path);

FileLock lock=channel.lock;

FileLock lcok=channel.tryLock();

FileLock lock(long start,long size,boolean shared)

FileLock lock(long start,long size,boolean shared)

try(FileLock lock=channel.lock()){..}

1.8 正则表达式

Pattern pattern=Pattern.compile(patternString);

Matcher matcher=pattern.matcher(input);

Pattern pattern=Pattern.compile(patternString,Pattern.CASE_INSENSITIVE+Pattern.UNICODE_CASE);

matcher.group(1)

while(matcher.find()){ String match=input.substring(matcher.start,matcher.end);}

$n

$

\$

String[] tokens=pattern.split(input);