FileInputStream class

FileInputStreamを使用して画像の読み込み
FileOutputSttreamを使用して画像の書き込み

public class Outer {
    public static void main(String[] args) {
        try {
            FileInputStream fis = new FileInputStream("C:\\dirtest\\cook.jpg");
            BufferedInputStream ibs = new BufferedInputStream(fis);
            FileOutputStream fos = new FileOutputStream("C:\\dirtest\\cookcpy.jpg");
            BufferedOutputStream bos = new BufferedOutputStream(fos);
            try(ibs;bos) {
                while(true) {
                    byte[] bt = ibs.readNBytes(1024);   //1024byte づつread
                    if(bt.length == 0) break;
                    bos.write(bt);
                    bos.flush();
                }
            }
        } catch (IOException ex ){
            ex.printStackTrace();
        }
    }
}