20220518_原始字节流与缓冲字节流，单字节，字节数组，四种组合复制1G大文件耗时案例

public class ByteBufferTimeUsageDemo2 {
    private static final String SRC_FILE = "D:\\TXYdownload\\install app\\ensp\\eNSP&CRT\\CE.img";
    private static final String DEST_FILE = "D:\\TXYdownload\\install app\\ensp";
    public static void main(String[] args) {
//        copy1();/**使用原始字节流，一个字节一个字节地复制1G的大文件, 耗时长到不能等*/
//        copy2();/**使用原始字节流按一个一个字节数组，复制1G的大文件，桶1024k用了9秒，8192用了2.4秒*/
//        copy3();/**使用缓冲字节流按一个一个字节，复制1G的大文件，用了40秒*/
        copy4();/**使用缓冲字节流按一个一个字节数组，复制1G的大文件，桶1024用时2.6秒，8192用了2.4秒*/

    }

    private static void copy4() {
        long startTime = System.currentTimeMillis();
        try (InputStream in = new FileInputStream(SRC_FILE);
             InputStream bin = new BufferedInputStream(in);
             OutputStream ou = new FileOutputStream(DEST_FILE+"new_CE.img");
             OutputStream bou = new BufferedOutputStream(ou);
             /**资源放在这，你不用操心最后刷新或者释放的事了*/
        ) {
            int num;/**返回的是每次读取到的字节数目*/
            byte[] bys = new byte[8192];/**每次读取到的字节会存入这个数组, 1024用时2.6秒，8192用了2.4秒*/
            while ((num = bin.read(bys)) != -1){
                bou.write(bys);
            }
            System.out.println("Copy is finished.");
        } catch (Exception e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        System.out.println("Buffered byte stream arr by arr time usage: "+(endTime-startTime)/1000.0+"s");
    }

    private static void copy3() {
        long startTime = System.currentTimeMillis();
        try (InputStream in = new FileInputStream(SRC_FILE);
             InputStream bin = new BufferedInputStream(in);
             OutputStream ou = new FileOutputStream(DEST_FILE+"new_CE.img");
             OutputStream bou = new BufferedOutputStream(ou);
             /**资源放在这，你不用操心最后刷新或者释放的事了*/
        ) {
            int num;/**读到的单字节，读完之后下一次返回-1，代表空*/

            while ((num = bin.read()) != -1){
                bou.write(num);/**你用缓冲，这里还是一个字节一个字节地注入，依然慢，只是能完成任务*/
            }
            System.out.println("Copy is finished.");
        } catch (Exception e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        System.out.println("Buffered byte stream one by one time usage: "+(endTime-startTime)/1000.0+"s");
    }

    private static void copy2() {
        long startTime = System.currentTimeMillis();
        try (InputStream in = new FileInputStream(SRC_FILE);
             OutputStream ou = new FileOutputStream(DEST_FILE+"new_CE.img");
             /**资源放在这，你不用操心最后刷新或者释放的事了*/
        ) {
            int num;/**返回的是每次读取到的字节数目*/
            byte[] bys = new byte[8192];/**每次读取到的字节会存入这个数组, 1024k用了9秒，8192用了2.4秒*/
            while ((num = in.read(bys)) != -1){
                ou.write(bys);
            }
            System.out.println("Copy is finished.");
        } catch (Exception e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        System.out.println("Original byte stream arr by arr time usage: "+(endTime-startTime)/1000.0+"s");
    }

    private static void copy1() {
        long startTime = System.currentTimeMillis();
        try (InputStream in = new FileInputStream(SRC_FILE);
             OutputStream ou = new FileOutputStream(DEST_FILE+"new_CE.img");
             /**资源放在这，你不用操心最后刷新或者释放的事了*/
        ) {
            int num;/**返回的是byte，但你完全可以用int来接*/
            while ((num = in.read()) != -1){
                ou.write(num);
            }
            System.out.println("Copy is finished.");
        } catch (Exception e) {
            e.printStackTrace();
        }
        long endTime = System.currentTimeMillis();
        System.out.println("Original byte stream one by one time usage: "+(endTime-startTime)/1000.0+"s");
    }


}