Java I/O深入学习之File和RandomAccessFile

public class FileDemo { 
public static void main(String[] args) throws IOException {
File dir = new File("f:/dirDemo");
System.out.println("dir exists: " + dir.exists());
dir.mkdirs();
System.out.println("dir exists: " + dir.exists());
if(dir.isFile()) {
System.out.println("dir is a file.");
}else if(dir.isDirectory()) {
System.out.println("dir is a directory");
}
File file = new File("f:/dirDemo/fileDemo"); 
System.out.println(
"\n Absolute path: " + file.getAbsolutePath() +
"\n Can read: " + file.canRead() + 
"\n Can write: " + file.canWrite() +
"\n getName: " + file.getName() +
"\n getParent: " + file.getParent() +
"\n getPath: " + file.getPath() +
"\n length: " + file.length() +
"\n lastModified: " + file.lastModified() +
"\n isExist: " + file.exists());
file.createNewFile();
System.out.println("is file exist: " + file.exists());
if(file.isFile()) {
System.out.println("file is a file.");
}else if(file.isDirectory()) {
System.out.println("file is a directory");
}
System.out.println();
for(String filename : dir.list()) {
System.out.println(filename);
}
} 
}

dir exists: false
dir exists: true
dir is a directory
Absolute path: f:\dirDemo\fileDemo
Can read: false
Can write: false
getName: fileDemo
getParent: f:\dirDemo
getPath: f:\dirDemo\fileDemo
length: 0
lastModified: 0
isExist: false
is file exist: true
file is a file.
fileDemo

public class XmlList { 
public static void main(final String[] args) {
File file = new File(".");
String list;
list = file.list(new FilenameFilter(){
@Override
public boolean accept(File dir, String name) {
Pattern pattern = Pattern.compile("(.*)\\.xml");
return pattern.matcher(name).matches();
}
});
Arrays.sort(list,String.CASE_INSENSITIVE_ORDER);
for(String dirItem : list)
System.out.println(dirItem);
}
}

public class Directory {
// local方法可以获得指定目录下指定文件的集合
public static File[] local(File dir,String regex) {
return dir.listFiles(new FilenameFilter() {
private Pattern pattern = Pattern.compile(regex);
@Override
public boolean accept(File dir, String name) {
return pattern.matcher(new File(name).getName()).matches();
}
});
}
public static File[] local(String dir,String regex) {
return local(new File(dir),regex);
}
// walk()方法可以获得指定目录下所有符合要求的文件或目录，包括子目录下
public static TreeInfo walk(String start,String regex) {
return recurseDirs(new File(start),regex);
}
public static TreeInfo walk(File start,String regex) {
return recurseDirs(start,regex);
}
public static TreeInfo walk(String start) {
return recurseDirs(new File(start),".*");
}
public static TreeInfo walk(File start) {
return recurseDirs(start,".*");
}
static TreeInfo recurseDirs(File startDir,String regex) {
TreeInfo treeInfo = new TreeInfo();
for(File item : startDir.listFiles()) {
if(item.isDirectory()) {
treeInfo.dirs.add(item);
treeInfo.addAll(recurseDirs(item,regex));
}else {
if(item.getName().matches(regex))
treeInfo.files.add(item);
}
}
return treeInfo;
}
public static class TreeInfo implements Iterable<File>{

public List<File> files = new ArrayList();
public List<File> dirs = new ArrayList();
@Override
public Iterator<File> iterator() {
return files.iterator();
}
void addAll(TreeInfo other) {
files.addAll(other.files);
dirs.addAll(other.dirs);
}
}
}

public class RandomAccessFileDemo { 
public static void main(String[] args) {
File file = new File("./test.txt");
if(!file.exists()) {
try {
file.createNewFile();
} catch (IOException e1) {
e1.printStackTrace();
}
}
RandomAccessFile raf = null;
try {
raf = new RandomAccessFile("./test.txt","rw");
raf.write(1000);
raf.seek(0);
System.out.println(raf.read());
raf.seek(0); 
System.out.println(raf.readInt());
} catch (FileNotFoundException e) {
System.out.println("file not found");
} catch (EOFException e) {
System.out.println("reachs end before read enough bytes");
e.printStackTrace();
} catch(IOException e) {
e.printStackTrace();
}finally {
try {
raf.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

232
reachs end before read enough bytes

public class RandomAccessFileDemo {
public static void main(String[] args) throws IOException {
File file = new File("f:/test.txt");
file.createNewFile();
// 创建临时空文件用于缓冲，并指定在虚拟机停止时将其删除
File temp = File.createTempFile("temp", null);
temp.deleteOnExit();
RandomAccessFile raf = null;
try {
// 首先往文件中写入下面的诗句，并读取出来在控制台打印
raf = new RandomAccessFile(file,"rw");
raf.write("明月几时有，把酒问青天".getBytes());
raf.seek(0); 
byte[] b = new byte[60];
raf.read(b, 0, 30);
System.out.println(new String(b));
// 接下来在诗句中间再插入一句诗
raf.seek(12);
FileOutputStream fos = new FileOutputStream(temp);
FileInputStream fis = new FileInputStream(temp);
byte[] buffer = new byte[10];
int num = 0;
while(-1 != (num = raf.read(buffer))) {
fos.write(buffer, 0, num);
}
raf.seek(12);
raf.write("但愿人长久，千里共婵娟。".getBytes());
// 插入完成后将缓冲的后半部分内容添加进来
while(-1 != (num = fis.read(buffer))) {
raf.write(buffer, 0, num);
}
raf.seek(0);
raf.read(b, 0, 60);
System.out.println(new String(b));
System.out.println();
} catch (FileNotFoundException e) {
e.printStackTrace();
}finally {
raf.close();
}
}
}

明月几时有，把酒问青天
明月几时有，但愿人长久，千里共婵娟。把酒问青天