java实现大文件的分割与合并

最近遇到一个问题，某网盘上传文件时，文件大小超过了4个G ，不能上传，所以就想到了利用的java的IO流，将文件分割成多个小文件，上传到网盘上，等到需要用的时候，下载下来然后再进行文件的合并就可以了。

这里以分割一个8.85M的PDF文件为例，分割成每个大小为1M的文件，分割文件的大小，只需修改size即可，代码如下：

1.文件的分割

public static void main(String[] args) throws IOException {
         
            //要分割出来的文件的大小
            int size = 1024*1024*1;//1M
             
            BufferedInputStream in = new BufferedInputStream(new FileInputStream(new File("D:\\zzy\\aaaa\\fileSplit\\java.pdf")));
            int len = -1;
            for (int i = 0; i < 9; i++) { //8.85M的文件分割成8个1M的，和一个0.85M的
                File file = new File("D:\\zzy\\aaaa\\fileSplit\\" + i + "temp.temp");//分割的文件格式可以随便设置，只要文件合并时名称一致即可
                FileOutputStream outputStream = new FileOutputStream(file);
                BufferedOutputStream out = new BufferedOutputStream(outputStream);
             
                int count = 0;
                byte[] bt = new byte[1024 * 1024];//每次读取1M,数组大小不能太大，会内存溢出，通过目标文件大小size判断一下
                while ((len = in.read(bt)) != -1) {
                 
                    out.write(bt, 0, len);
                    count += len;
                    if(count>=size) {
                        break;//每次读取1M，然后写入到文件中
                    }
                }
             
                out.flush();
                out.close();
                outputStream.close();
             
                System.out.println("文件已完成：" + file.getName());
            }
     
            System.out.println("文件已完成分割====");
        }

2.文件的合并

public static void main(String[] args) throws IOException {
             
        //文件合并
 
            BufferedOutputStream out = new BufferedOutputStream(
                    new FileOutputStream(new File("D:\\zzy\\aaaa\\fileSplit\\java(merge).pdf")));
             
            for (int i = 0; i < 9; i++) { //9个文件合并成8.85M的文件
                File file = new File("D:\\zzy\\aaaa\\fileSplit\\" + i + "temp.temp");
                FileInputStream inputStream = new FileInputStream(file);
                BufferedInputStream in = new BufferedInputStream(inputStream);
                 
                int len = -1;
                byte[] bt = new byte[1024 * 1024];//每次读取1M,数组大小不能太大，会内存溢出
                while ((len = in.read(bt)) != -1) {
                 
                    out.write(bt, 0, len);
                }
             
                in.close();
                inputStream.close();
                out.flush();
             
                System.out.println("文件已完成：" + file.getName());
            }
         
            System.out.println("文件已完成合并====");
        }            