读取各种编码的text文件

public static void main(String[] args) throws IOException {
File file = new File("d:/java思考Unicode big endian.txt");
InputStream inputStream = new FileInputStream(file);  
        byte[] head = new byte[3];  
        inputStream.read(head);   
        String code = "gb2312";  
        if (head[0] == -1 && head[1] == -2 )
        {
        code = "UTF-16";  
        }
        if (head[0] == -2 && head[1] == -1 )
        {
        code = "Unicode";  
        }
        if(head[0]==-17 && head[1]==-69 && head[2] ==-65)
        {
        code = "UTF-8";  
        }
        System.out.println(code); 
BufferedReader br=new BufferedReader(new InputStreamReader(new FileInputStream(file), code));
String str="";
String r=br.readLine();
while(r!=null){
str+=r+"\r";
r=br.readLine();
}
System.out.println(str);
}