Java -- IO
1. 文件过滤器
public class Main {
public static void main(String[] args) throws IOException
{
File file = new File("/home/test/");
String [] nameList = file.list(new FilenameFilter() { //文件过滤器
@Override
public boolean accept(File dir, String name) {
// TODO Auto-generated method stub
return name.endsWith(".png")
|| new File(name).isDirectory(); //后缀名"png"， 或者是目录
}
});
for(String str : nameList )
{
System.out.println(str);
}
}
}
2. 整理
// * write by kevin, 2013/7/8
import java.io.*;
public class IO_test {
public boolean IsExist(String fileName){ //文件是否存在
File file = new File(fileName);
if( file.exists() ){
System.out.println("Is file: " + file.isFile());
System.out.println("Filename is: " + file.getName());
System.out.println("Path is: " + file.getPath());
System.out.println("AbsolutePath " + file.getAbsolutePath());
System.out.println("Parent dir is: " + file.getParent());
System.out.println("File size is: " + file.length() + " bytes");
return true;
}
else{
return false;
}
}
public boolean CreateFile(String fileName) throws IOException{ //创建文件
File file = new File(fileName);
if( file.exists() ){
System.out.println(fileName + " File has existed");
return false;
}
else{
file.createNewFile();
return true;
}
}
public boolean CreateDir(String dirName){ //创建目录
File file = new File(dirName);
if( file.exists() ){
System.out.println(dirName + " Dir has existed");
return false;
}
else{
file.mkdirs();
return true;
}
}
public void WriteByByte(String fileName, String str) throws IOException{ //以字节流写文件
File file = new File(fileName);
if( !file.exists() )
{
System.out.println(fileName + " File doesn't exist");
file.createNewFile();
System.out.println(fileName + " File has created");
}
FileOutputStream fo = new FileOutputStream(file);
byte [] content = str.getBytes();
fo.write(content);
fo.close();
}
public String ReadByByte(String fileName) throws IOException{ //以字节流读文件
File file = new File(fileName);
if ( file.exists() ){
FileInputStream fi = new FileInputStream(file);
byte [] content = new byte[fi.available()];
fi.read(content);
String str = new String(content);
System.out.println("Read file: " + str.trim());
fi.close();
return str.trim();
}
else{
System.out.println("File doesn't exist");
return "File doesn't exist";
}
}
public String ReadByBuffer(String fileName) throws IOException{ //以缓存的方式读文件
File file_temp = new File(fileName);
if ( file_temp.exists() ){
FileReader file = new FileReader(fileName);
BufferedReader br = new BufferedReader(file);
StringBuffer str = new StringBuffer();
String sw = br.readLine();
while( sw != null ){
str.append(sw + "\n");
sw = br.readLine();
}
System.out.println("Read file: " + str);
return str.toString();
}
else{
System.out.println("File doesn't exist");
return "File doesn't exist";
}
}
public void WriteByBuffer(String fileName, String str) throws IOException{ //以缓存方式写文件
File file_temp = new File(fileName);
if ( !file_temp.exists() ){
System.out.println(fileName + " File doesn't exist");
file_temp.createNewFile();
System.out.println(fileName + " File has created");
}
FileWriter file = new FileWriter(fileName);
BufferedWriter bw = new BufferedWriter(file);
bw.write(str);
bw.close();
}
public boolean DeleteFile(String fileName){ //删除文件
File file = new File(fileName);
if( file.exists() ){
System.out.println("Will delete file: " + fileName);
if( file.delete() ){
System.out.println("Have deleted file");
return true;
}
else{
System.out.println("Deleted file fail");
return false;
}
}
else{
System.out.println("File doesn't exist");
return false;
}
}
public boolean CopyFileByByte(String fileName1, String fileName2) throws IOException{ //以字节流 复制文件
File file = new File(fileName1);
if( !file.exists() ){
System.out.println(fileName1 + " File doesn't exist");
return false;
}
FileInputStream fi = new FileInputStream(file);
byte [] content = new byte[fi.available()];
fi.read(content);
fi.read(content, 0, content.length);
String str = new String(content);
File file_other =new File(fileName2);
if( !file_other.exists() ){
System.out.println(fileName2 + "File doesn't exist");
file_other.createNewFile();
System.out.println(fileName2 + "File has created");
}
FileOutputStream fo = new FileOutputStream (file_other,true);
fo.write(content);
fo.flush();
fo.close();
fi.close();
return true;
}
public boolean CopyFileByBuffer(String fileName1, String fileName2) throws IOException{ //以缓存方式复制文件
File file_temp = new File(fileName1);
if( !file_temp.exists() ){
System.out.println(fileName1 + "File doesn't existed");
return false;
}
file_temp = new File(fileName2);
if( !file_temp.exists() ){
System.out.println(fileName2 + "File doesn't existed");
file_temp.createNewFile();
System.out.println(fileName2 + "File has created");
}
FileReader file = new FileReader(fileName1);
BufferedReader br = new BufferedReader(file);
String str = br.readLine();
FileWriter file_other = new FileWriter(fileName2);
BufferedWriter bw = new BufferedWriter(file_other);
while( str!=null ){
bw.write(str);
bw.newLine();
str = br.readLine();
}
bw.flush();
bw.close();
br.close();
return false;
}
}
3. 重定义标准输入输出， 标准输入输出为键盘和屏幕，但是这些都可以自己重定义 为 文件 或其他
PrintStream ps = null;
try
{
ps = new PrintStream(new FileOutputStream("/home/test/123.txt"));
System.setOut(ps); //重定义标准输出到 文件123.txt
System.out.println("123456789");
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
ps.close();
}
FileInputStream fis = null;
try
{
fis = new FileInputStream("/home/test/123.txt");
System.setIn(fis); //重定义标准输入为 文件123.txt
Scanner sc = new Scanner(System.in);
sc.useDelimiter("\n");
while(sc.hasNext())
{
System.out.println(sc.next());
}
}
catch(IOException e)
{
e.printStackTrace();
}
finally
{
fis.close();
}
3. RandomAccessFile 读写文件， 可以操控指针，做到追加和插入文件内容。
public class Main {
public static void main(String[] args) throws IOException
{
RandomAccessFile raf = null;
try
{
raf = new RandomAccessFile("/home/test/123.txt", "rw");
System.out.println("point at: " + raf.getFilePointer());
raf.seek(5);
System.out.println("point at: " + raf.getFilePointer());
byte[] buf = new byte[512];
int hasRead = 0;
while( (hasRead=raf.read(buf)) > 0 )
{
System.out.println(new String(buf, 0, hasRead));
}
System.out.println("point at: " + raf.getFilePointer());
raf.write("add into file\n".getBytes());
}
catch (IOException e)
{
e.printStackTrace();
}
finally
{
raf.close();
}
}
}
4. 保存对象到文件， 对象序列化和反序列化
当使用Java序列化机制序列化可变对象时一定要要注意，只有当第一次调用writeObject方法来输出对象时才会将对象转为字节序列，第二次只会存入一个序列化编号。
class Person implements java.io.Serializable //序列化的类 需要实现Serializable接口
{
private String name;
private int age;
public Person(String name, int age)
{
this.name = name;
this.age = age;
}
int getAge()
{
return this.age;
}
String getName()
{
return this.name;
}
}
public class Main {
public static void main(String[] args)
{
ObjectOutputStream oos = null;
ObjectInputStream ois = null;
try
{
oos = new ObjectOutputStream(new FileOutputStream("/home/test/object.txt")); //对象输入流
Person per = new Person("kevin", 11);
oos.writeObject(per); //将对象写入流
try
{
oos.close();
}
catch( IOException e )
{
e.printStackTrace();
}
ois = new ObjectInputStream(new FileInputStream("/home/test/object.txt")); //对象反序列
Person p = (Person)ois.readObject(); //反序列
System.out.println("Get object from file, name: " + p.getName() + " age: " + p.getAge());
}
catch (IOException e)
{
e.printStackTrace();
}
catch (ClassNotFoundException e) {
e.printStackTrace();
}
finally
{
try
{
ois.close();
}
catch( IOException e )
{
e.printStackTrace();
}
}
}
}
5. 文件锁
FileOutputStream fos = new FileOutputStream("file.txt");
