import java.io.BufferedReader;  
import java.io.File;  
import java.io.FileInputStream;  
import java.io.InputStream;  
import java.io.InputStreamReader;  
  
public class read_file {  
    public static void main(String[] args) throws Exception {  
        String filePath = "g:\\aaa\\789.txt";  
        String content = readTxt(filePath);  
        System.out.println(content);  
          
    }  
    /** 
     * 解析普通文本文件  流式文件 如txt 
     * @param path 
     * @return 
     */  
    @SuppressWarnings("unused")  
    public static String readTxt(String path){  
        StringBuilder content = new StringBuilder("");  
        try {  
            String code = resolveCode(path);  
            File file = new File(path);  
            InputStream is = new FileInputStream(file);  
            InputStreamReader isr = new InputStreamReader(is, code);  
            BufferedReader br = new BufferedReader(isr);  
            String str = "";  
            while (null != (str = br.readLine())) {  
                content.append(str);  
            }  
            br.close();  
        } catch (Exception e) {  
            e.printStackTrace();  
            System.err.println("读取文件:" + path + "失败!");  
        }  
        return content.toString();  
    }  
    public static String resolveCode(String path) throws Exception {  
        InputStream inputStream = new FileInputStream(path);    
        byte[] head = new byte[3];    
        inputStream.read(head);      
        String code = "gb2312";  //或GBK  
        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"; 
        inputStream.close();  
        return code;  
    }  
      
}