IO stream operation 1: copy the source file/source folder to the specified directory

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * IO operation
 * 1. Pay attention to appending and overwriting
 * 2. Streams can only operate on files
 * 3. Stream closing rules: first open and then close
 * 4.read(): Returns the length of bytes currently read
 * 5. Common grammar
 *  	File file = new File(String path);
 *  	File file = new File(String parent, String child);
 *  	File file = new File(File parent, String child);
 *  	InputStream = new FileInputStream(String path);
 *  	InputStream = new FileInputStream(String path, boolean flag);
 *  	InputStream = new FileInputStream(File file);
 *  	InputStream = new FileInputStream(File file, boolean flag);
 * @author pengjunzhao
 * @date December 25, 2017
 */
public class MyIO {
	public static void main(String[] args) throws IOException {
		//Folder copy (recursive)
		directoryCopy("G:/other/2.jpg", "G:/download");
	}
	
	/**
	 * Folder copy
	 * @param srcPath source folder path
	 * @param destPath destination folder path
	 * @throws IOException
	 */
	public static void directoryCopy(String srcPath, String destPath) throws IOException{
		File src = new File(srcPath);
		File dest = new File(destPath);
		//1. Whether the target folder exists and is a directory, if not, create it
		if(!dest.exists() && dest.isDirectory()){
			dest.mkdirs ();
		}else if(dest.isFile()){
			System.out.println("The destination folder path cannot be a file type");
			return;
		}
		// start copying
		directoryCopyDetail(src, dest);
	}
	
	//Folder copy details
	public static void directoryCopyDetail(File src, File dest) throws IOException{
		//2. The source target is a folder and the folder is created if it does not exist in the sub-directory of the target file
		File newFile = new File(dest, src.getName());
		if(src.isDirectory()){
			newFile.mkdirs(); //Create a new directory in the target folder
			for(File sub:src.listFiles()){
				//3. Traverse the folder, copy the file if it is, and call this method repeatedly if it is the directory
				directoryCopyDetail(sub, newFile);
			}
		}else if(src.isFile()){
			fileCopy(src, newFile); //Create a file in the target folder
		}
	}
	
	/**
	 * file copy
	 * @param srcPath
	 * @param destPath
	 * @throws IOException
	 */
 	public static void fileCopy(File srcPath, File destPath) throws IOException{
 		if(!srcPath.isFile()){
 			System.out.println("The source path is not a file type");
 			return;
 		}
		/*
		 * There is no need to judge destPath here
		 * Because: When the program outputs to a file, the file is created directly if and only if the file does not exist. An error will be reported when the parent directory of the file does not exist
		 */
 		//4. Stream implements file content copying
		InputStream is = new FileInputStream(srcPath); //input stream, write program from file
		OutputStream os = new FileOutputStream(destPath, false); //Output stream, output from program to file (hard disk). true means append write operation (default overwrite)
		byte[] bt = new byte[1024];
		int len ​​= 0; // current number of bytes read
		// read sequentially
		while(-1 != (len=is.read(bt, 0 ,1024))){
			// write sequentially
			os.write (bt, 0, len);
		}
		os.flush();
		os.close();
		is.close();
	}	
}