文件拷贝

import java.io.*;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;

public class NIOFileReadAndWrite {
    private String file;

    public String getFile() {
        return file;
    }

    public void setFile(String file) {
        this.file = file;
    }

    public NIOFileReadAndWrite(String file) throws IOException {
        super();
        this.file = file;
    }

    /**
     * NIO读取文件
     * @param allocate
     * @throws IOException
     */
    public void read(int allocate) throws IOException {

        RandomAccessFile access = new RandomAccessFile(this.file, "r");

        //FileInputStream inputStream = new FileInputStream(this.file);
        FileChannel channel = access.getChannel();
        ByteBuffer byteBuffer = ByteBuffer.allocate(allocate);

        CharBuffer charBuffer = CharBuffer.allocate(allocate);
        Charset charset = Charset.forName("GBK");
        CharsetDecoder decoder = charset.newDecoder();
        int length = channel.read(byteBuffer);
        while (length != -1) {
            byteBuffer.flip();
            decoder.decode(byteBuffer, charBuffer, true);
            charBuffer.flip();
            System.out.println(charBuffer.toString());
            // 清空缓存
            byteBuffer.clear();
            charBuffer.clear();
            // 再次读取文本内容
            length = channel.read(byteBuffer);
        }
        channel.close();
        if (access != null) {
            access.close();
        }
    }

    /**
     * NIO写文件
     * @param context
     * @param allocate
     * @param chartName
     * @throws IOException
     */
    public void write(String context, int allocate, String chartName) throws IOException{
        // FileOutputStream outputStream = new FileOutputStream(this.file); //文件内容覆盖模式 --不推荐
        FileOutputStream outputStream = new FileOutputStream(this.file, true); //文件内容追加模式--推荐
        FileChannel channel = outputStream.getChannel();
        ByteBuffer byteBuffer = ByteBuffer.allocate(allocate);
        byteBuffer.put(context.getBytes(chartName));
        byteBuffer.flip();//读取模式转换为写入模式
        channel.write(byteBuffer);
        channel.close();
        if(outputStream != null){
            outputStream.close();
        }
    }

    /**
     * nio事实现文件拷贝
     * @param source
     * @param target
     * @param allocate
     * @throws IOException
     */
    public static void nioCpoy(String source, String target, int allocate) throws IOException{
        ByteBuffer byteBuffer = ByteBuffer.allocate(allocate);
        FileInputStream inputStream = new FileInputStream(source);
        FileChannel inChannel = inputStream.getChannel();

        FileOutputStream outputStream = new FileOutputStream(target);
        FileChannel outChannel = outputStream.getChannel();

        int length = inChannel.read(byteBuffer);
        while(length != -1){
            byteBuffer.flip();//读取模式转换写入模式
            outChannel.write(byteBuffer);
            byteBuffer.clear(); //清空缓存，等待下次写入
            // 再次读取文本内容
            length = inChannel.read(byteBuffer);
        }
        outputStream.close();
        outChannel.close();
        inputStream.close();
        inChannel.close();
    }

    public static void fileChannelCopy(String sfPath, String tfPath) {

        File sf = new File(sfPath);
        File tf = new File(tfPath);
        FileInputStream fi = null;
        FileOutputStream fo = null;
        FileChannel in = null;
        FileChannel out = null;
        try{
            fi = new FileInputStream(sf);
            fo = new FileOutputStream(tf);
            in = fi.getChannel();//得到对应的文件通道
            out = fo.getChannel();//得到对应的文件通道
            in.transferTo(0, in.size(), out);//连接两个通道，并且从in通道读取，然后写入out通道
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            try{
                fi.close();
                in.close();
                fo.close();
                out.close();
            }catch (Exception e){
                e.printStackTrace();
            }
        }
    }


    //IO方法实现文件k拷贝
    private static void traditionalCopy(String sourcePath, String destPath) throws Exception {
        File source = new File(sourcePath);
        File dest = new File(destPath);
        if (!dest.exists()) {
            dest.createNewFile();
        }
        FileInputStream fis = new FileInputStream(source);
        FileOutputStream fos = new FileOutputStream(dest);
        byte[] buf = new byte[1024];
        int len = 0;
        while ((len = fis.read(buf)) != -1) {
            fos.write(buf, 0, len);
        }
        fis.close();
        fos.close();
    }

    public static void main(String[] args) throws Exception{


        long start = System.currentTimeMillis();
        nioCpoy("D:\\迅雷下载\\jdk-21_windows-x64_bin.zip", "D:\\qwe\\jdk-21_windows-x64_bin.zip",10240);
        long end = System.currentTimeMillis();
        System.out.println("用时为：" + (end-start));

        long start2 = System.currentTimeMillis();
        fileChannelCopy("D:\\迅雷下载\\jdk-21_windows-x64_bin.zip", "D:\\qwe\\jdk-21_windows-x64_bin.zip");
        long end2 = System.currentTimeMillis();
        System.out.println("用时为：" + (end2-start2));

        long start3 = System.currentTimeMillis();
        traditionalCopy("D:\\迅雷下载\\jdk-21_windows-x64_bin.zip", "D:\\qwe\\jdk-21_windows-x64_bin.zip");
        long end3 = System.currentTimeMillis();
        System.out.println("用时为：" + (end3-start3));
    }

}