新io练习

刚刚复习了一下java新io,备份一下！

这个是手动写通过管道来复制文件

public class ChannelCopy {

    private static final int BSIZE = 1024;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {
            File file = new File("D:/dta.txt");
            File daf = new File("D:/data.txt");
            FileChannel in = new FileInputStream(file).getChannel();
            FileChannel out = new FileOutputStream(daf).getChannel();           
            ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
            while (in.read(buffer) != -1) {
                buffer.flip();
                out.write(buffer);
                buffer.clear();
            }
        } catch (Exception ex) {
            Logger.getLogger(ChannelCopy.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

效率更高的方式：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.channels.FileChannel;
import java.util.logging.Level;
import java.util.logging.Logger;

public class ChannelCopy {

    private static final int BSIZE = 1024;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {
            File file = new File("D:/dta.txt");
            File daf = new File("D:/data.txt");
            FileChannel in = new FileInputStream(file).getChannel();
            FileChannel out = new FileOutputStream(daf).getChannel();    
            in.transferTo(0, in.size(), out);
            //or
//            out.transferFrom(in, 0, in.size());
        } catch (Exception ex) {
            Logger.getLogger(ChannelCopy.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}

 

ByteBuffer练习：

public class App {

    public static void main(String[] args) throws IOException {
        //write a file
        File file = new File("D:/dta.txt");
        System.out.println("file is exist:"+file.exists());
        FileChannel fc = new FileOutputStream(file).getChannel();
        fc.position(fc.size());
        fc.write(ByteBuffer.wrap("Some more 123456".getBytes()));
        fc.close();
        
        //add to the end of the file
        fc=new RandomAccessFile(file, "rw").getChannel();
        fc.position(fc.size());//move to the end
        fc.write(ByteBuffer.wrap("TestSome more".getBytes()));
        fc.close();
        
        //read the file
        fc=new FileInputStream(file).getChannel();
        ByteBuffer buffer = ByteBuffer.allocate(1024);
        fc.read(buffer);
        buffer.flip();
        
        while(buffer.hasRemaining()){
            System.out.println((char)buffer.get());
        }
    }
}

 

设置编码格式：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.util.logging.Level;
import java.util.logging.Logger;

public class BufferToText {

    private static final int BSIZE = 1024;

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        try {
            File file = new File("D:/dta.txt");
            File fileOut = new File("D:/data.txt");
            FileChannel fc = new FileOutputStream(fileOut).getChannel();
            fc.write(ByteBuffer.wrap("Some text".getBytes()));
            fc.close();
            fc = new FileInputStream(fileOut).getChannel();
            ByteBuffer buffer = ByteBuffer.allocate(BSIZE);
            fc.read(buffer);
            buffer.flip();
            //Doesn't work,这里打印出来出现乱码：卯浥?數
            System.out.println(buffer.asCharBuffer());
            
            //Decode using this System's default Charset
            buffer.rewind();
            String encoding = System.getProperty("file.encoding");
            System.out.println("Decoded using "+encoding+" : "+Charset.forName(encoding).decode(buffer));
            
            //Or,we could encode with something that will print
            fc = new FileOutputStream(fileOut).getChannel();
            fc.write(ByteBuffer.wrap("Some text 1234".getBytes("UTF-16BE")));
            fc.close();
            
            //Now try reading again
            fc= new FileInputStream(fileOut).getChannel();
            buffer.clear();
            fc.read(buffer);
            buffer.flip();
            System.out.println(buffer.asCharBuffer());
            
            //Use a CharBuffer to write through
            fc= new FileOutputStream(fileOut).getChannel();
            buffer = ByteBuffer.allocate(24);
            buffer.asCharBuffer().put("Some text ttererer");
            fc.write(buffer);
            fc.close();
            
            //Read and display
            fc= new FileInputStream(fileOut).getChannel();
            buffer.clear();
            fc.read(buffer);
            buffer.flip();
            System.out.println("Read and display");
            System.out.println(buffer.asCharBuffer());
        } catch (Exception ex) {
            Logger.getLogger(BufferToText.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
}