Java获取字符串编码格式实现思路

    public static String getEncoding(String str) {
        String encode = "GB2312";
        try {
            if (isEncoding(str, encode)) { // 判断是不是GB2312
                return encode;
            }
        } catch (Exception exception) {
        }
        encode = "ISO-8859-1";
        try {
            if (isEncoding(str, encode)) { // 判断是不是ISO-8859-1
                return encode;
            }
        } catch (Exception exception1) {
        }
        encode = "UTF-8";
        try {
            if (isEncoding(str, encode)) { // 判断是不是UTF-8
                return encode;
            }
        } catch (Exception exception2) {
        }
        encode = "GBK";
        try {
            if (isEncoding(str, encode)) { // 判断是不是GBK
                return encode;
            }
        } catch (Exception exception3) {
        }
        return ""; // 如果都不是，说明输入的内容不属于常见的编码格式。
    }

    public static boolean isEncoding(String str, String encode) {
        try {
            if (str.equals(new String(str.getBytes(), encode))) {
                return true;
            }
        } catch (UnsupportedEncodingException e) {
            e.printStackTrace();
        }
        return false;
    }

package com.java265.other;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStream;
 
public class Test {
    
     
    public static void main(String[] args)   {
      File file = new File("E://person/java265.com/java.txt");
      System.out.println(GetEncoding(file));
      }
    public static String GetEncoding(File file)
    {
        String charset = "GBK";
        byte[] first3Bytes = new byte[3];
        try {
            boolean checked = false; 
            InputStream is = new FileInputStream(file);
            int read = is.read(first3Bytes, 0, 3);
 
            if (read == -1)
                return charset;
            if (first3Bytes[0] == (byte) 0xFF && first3Bytes[1] == (byte) 0xFE) {
                charset = "UTF-16LE";
                checked = true;
            } else if (first3Bytes[0] == (byte) 0xFE
                    && first3Bytes[1] == (byte) 0xFF) {
                charset = "UTF-16BE";
                checked = true;
            } else if (first3Bytes[0] == (byte) 0xEF
                    && first3Bytes[1] == (byte) 0xBB
                    && first3Bytes[2] == (byte) 0xBF) {
                charset = "UTF-8";
                checked = true;
            }else if (first3Bytes[0] == (byte) 0xA
                    && first3Bytes[1] == (byte) 0x5B
                    && first3Bytes[2] == (byte) 0x30) {
                charset = "UTF-8";
                checked = true;
            }else if (first3Bytes[0] == (byte) 0xD
                    && first3Bytes[1] == (byte) 0xA
                    && first3Bytes[2] == (byte) 0x5B) {
                charset = "GBK";
                checked = true;
            }else if (first3Bytes[0] == (byte) 0x5B
                    && first3Bytes[1] == (byte) 0x54
                    && first3Bytes[2] == (byte) 0x49) {
                charset = "windows-1251";
                checked = true;
            }
            //bis.reset();
            InputStream istmp = new FileInputStream(file);
            if (!checked) {
                int loc = 0;
                while ((read = istmp.read()) != -1) {
                    loc++;
                    if (read >= 0xF0)
                        break;
                    if (0x80 <= read && read <= 0xBF)
                        break;
                    if (0xC0 <= read && read <= 0xDF) {
                        read = istmp.read();
                        if (0x80 <= read && read <= 0xBF)
                            continue;
                        else
                            break;
                    } else if (0xE0 <= read && read <= 0xEF) {
                        read = istmp.read();
                        if (0x80 <= read && read <= 0xBF) {
                            read = istmp.read();
                            if (0x80 <= read && read <= 0xBF) {
                                charset = "UTF-8";
                                break;
                            } else
                                break;
                        } else
                            break;
                    }
                }
            }
            is.close();
            istmp.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return charset; 
    }
}