String path = "E:/temp/logcat/01_testcase/bbb.txt";
InputStream inputStream = new FileInputStream(path);
byte[] head = new byte[300];
inputStream.read(head);
String code = "";
System.out.print(" " + head[0]);
System.out.print(" " + head[1]);
System.out.println(" " + head[3]);
if (head[0] == -1 && head[1] == -2) {
code = "UTF-16";
} else if (head[0] == -2 && head[1] == -1) {
code = "Unicode";
} else if (head[0] == -17 && head[1] == -69 && head[2] == -65) {
code = "UTF-8";
}
bbb.txt中的内容是abcd
运行结果：head[0]=97 head[1]=98 head[2]=100
head的运行结果并不是预期的 -17 -69 -65. 这是什么原因啊？
普通文件，开始就是文件内容了。
有编码的，开头先是编码的定义，正如判断语句所写的那样追问
1、什么样的文件不是普通文件？右键新建文本文档是普通文件？
2、有2个文件：aaa.txt bbb.txt
在本机双击打开时，aaa.txt默认编码是UTF-8 bbb.txt默认编码是GB2312
用上面的程序运行时 都不能获取正确的编码。
最标准的途径是检测文本最开头的几个字节，开头字节 Charset/encoding,如下表：
EF BB BF UTF-8
FE FF UTF-16/UCS-2, little endian
FF FE UTF-16/UCS-2, big endian
FF FE 00 00 UTF-32/UCS-4, little endian.
00 00 FE FF UTF-32/UCS-4, big-endian.
int[] head = new int[4];
InputStream inputStream = new FileInputStream(path);
for(int i=0; i<4; i++){
head[0]=inputStream.read();
}
inputStream.close();
String code = "ANSI";
if (head[0]==0xef && head[1]==0xbb && head[2]==0xbf) {
code = "UTF-8";
} else if(head[0]==0xfe && head[1]==0xff) {
code = "utf-16/ucs2, little endian";
} else if(head[0]==0xff && head[1]==0xfe) {
code = "utf-16/ucs2, big endian";
} else if(head[0]==0xff && head[1]==0xfe && head[2]==0x0 && head[3]==0x0) {
code = "UTF-32/ucs4, little endian";
} else if (head[0]==0x0 && head[1]==0x0 && head[2]==0xfe && head[3]==0xff) {
code = "UTF-32/ucs4, big endian";
}
