Use filechannel to copy files

package com.yanchi;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

/** * @author yanchi * @date 2022/6/30 14:04 */
public class FileChannelTest {
    
    public static void main(String[] args) {
    
        try (
                FileChannel from = new FileInputStream("data.txt").getChannel();
                FileChannel to = new FileOutputStream("to.txt").getChannel();
        ) {
    
        	//  The maximum transmission at one time  2g
            from.transferTo(0,from.size(),to);
        } catch (IOException e) {
    
            e.printStackTrace();
        }
    }
}

Because the above method can only transmit 2G The file of , The following code optimizes the above code ！！

package com.yanchi;

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

/** * @author yanchi * @date 2022/6/30 14:04 */
public class FileChannelTest {
    
    public static void main(String[] args) {
    
        try (
                FileChannel from = new FileInputStream("data.txt").getChannel();
                FileChannel to = new FileOutputStream("to.txt").getChannel();
        ) {
    
            //  Bytes of source file 
            long size = from.size();
            // left  Represents how many bytes are left 
            for (long left = size; left > 0;){
    
                left -= from.transferTo((size - left), left, to);
            }
        } catch (IOException e) {
    
            e.printStackTrace();
        }
    }
}