在Java中,提供了四种类来对文件进行操作,分别是InputStream OutputStream Reader Writer ,前两种是对字节流的操作,后两种则是对字符流的操作。
示例代码如下:
public static void readFileByBytes(String fileName){
File file = new File(fileName)
InputStream in = null
try {
System.out.println("一次读一个")
// 一次读一个字节
in = new FileInputStream(file)
int tempbyte
while ((tempbyte = in.read()) != -1) {
System.out.write(tempbyte)
}
in.close()
} catch (IOException e) {
e.printStackTrace()
return
}
Java中将图片转为二进制流只需要使用FileImageInputStream取得图片文件,然后使用ByteArrayOutputStream 写入到二进制流中即可,下面是详细代码:
//图片到byte数组
public byte[] image2byte(String path){
byte[] data = null
FileImageInputStream input = null
try {
input = new FileImageInputStream(new File(path))
ByteArrayOutputStream output = new ByteArrayOutputStream()
byte[] buf = new byte[1024]
int numBytesRead = 0
while ((numBytesRead = input.read(buf)) != -1) {
output.write(buf, 0, numBytesRead)
}
data = output.toByteArray()
output.close()
input.close()
}
catch (FileNotFoundException ex1) {
ex1.printStackTrace()
}
catch (IOException ex1) {
ex1.printStackTrace()
}
return data
}
另外,如果需要将byte[]存回图片或转为String,则:
//byte数组到图片public void byte2image(byte[] data,String path){
if(data.length<3||path.equals("")) return
try{
FileImageOutputStream imageOutput = new FileImageOutputStream(new File(path))
imageOutput.write(data, 0, data.length)
imageOutput.close()
System.out.println("Make Picture success,Please find image in " + path)
} catch(Exception ex) {
System.out.println("Exception: " + ex)
ex.printStackTrace()
}
}
//byte数组到16进制字符串
public String byte2string(byte[] data){
if(data==null||data.length<=1) return "0x"
if(data.length>200000) return "0x"
StringBuffer sb = new StringBuffer()
int buf[] = new int[data.length]
//byte数组转化成十进制
for(int k=0k<data.lengthk++){
buf[k] = data[k]<0?(data[k]+256):(data[k])
}
//十进制转化成十六进制
for(int k=0k<buf.lengthk++){
if(buf[k]<16) sb.append("0"+Integer.toHexString(buf[k]))
else sb.append(Integer.toHexString(buf[k]))
}
return "0x"+sb.toString().toUpperCase()
}