1、将File、FileInputStream 转换为byte数组：

File file = new File("test.txt");

InputStream input = new FileInputStream(file);

byte[] byt = new byte[input.available()];

input.read(byt);

2、将byte数组转换为InputStream：

byte[] byt = new byte[1024];

InputStream input = new ByteArrayInputStream(byt);

3、将byte数组转换为File：

File file = new File(‘‘);

OutputStream output = new FileOutputStream(file);

BufferedOutputStream bufferedOutput = new BufferedOutputStream(output);

bufferedOutput.write(byt);

java 中 byte[]、File、InputStream 互相转换