java BufferedReader 读取文件 乱码，求解,该怎么解决

File file = new File("D:/aa.cer");InputStreamReader isr;isr = new InputStreamReader(new FileInputStream(file),"utf-8");String line=null;while((line=bf.readLine())!=null){    System.out.print(line);}

File file = new File("D:/aa.cer");        FileReader fr=null;        try {            fr = new FileReader(file);            char[] temp=new char[(int) file.length()];            fr.read(temp);            fr.close();            System.out.println(new String(temp));        } catch (FileNotFoundException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }
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你确定你的D:/aa.cer文件时utf-8编码的吗？

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探讨

不知道文件是什么编码的？这样要怎么解决的

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可以测试文件的编码，然后根据编码来打开文件的：http://blog.csdn.net/wula0010/article/details/6862696
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分别调用下面的两个方法，看看输出什么

Java code
public static void readGBKCodingFile(String fileName) {//读取GBK文件的内容        BufferedReader br = null;        try {            br = new BufferedReader(new InputStreamReader(new FileInputStream(                    fileName), "gbk"));            String line = null;            while ((line = br.readLine()) != null) {                System.out.println(line);            }        } catch (Exception e) {        } finally {            try {                if (br != null)                    br.close();            } catch (IOException e) {            }        }    }            public static void readUTFCodingFile(String fileName) {//读取UTF-8文件的内容        BufferedReader br = null;        try {            br = new BufferedReader(new InputStreamReader(new FileInputStream(                    fileName), "utf-8"));            String line = null;            while ((line = br.readLine()) != null) {                System.out.println(line);            }        } catch (Exception e) {        } finally {            try {                if (br != null)                    br.close();            } catch (IOException e) {            }        }    }
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你想转化文件格式，试试下面的两个方法
Java code
    public static void convertGBKFileToUTFFile(String srcFileName, String destFileName) {//把GBK文件转换为UTF文件        BufferedReader br = null;        ;        BufferedWriter bw = null;        try {            br = new BufferedReader(new InputStreamReader(new FileInputStream(                    srcFileName), "gbk"));            bw = new BufferedWriter(new OutputStreamWriter(                    new FileOutputStream(destFileName), "UTF-8"));            String line = null;            while ((line = br.readLine()) != null) {                bw.write(line);                bw.newLine();            }        } catch (Exception e) {        } finally {            try {                if (br != null)                    br.close();                if (bw != null)                    bw.close();            } catch (IOException e) {            }        }    }        public static void convertUTFFileToGBKFile(String srcFileName, String destFileName) {//把GBK文件转换为UTF文件        BufferedReader br = null;        ;        BufferedWriter bw = null;        try {            br = new BufferedReader(new InputStreamReader(new FileInputStream(                    srcFileName), "utf-8"));            bw = new BufferedWriter(new OutputStreamWriter(                    new FileOutputStream(destFileName), "gbk"));            String line = null;            while ((line = br.readLine()) != null) {                bw.write(line);                bw.newLine();            }        } catch (Exception e) {        } finally {            try {                if (br != null)                    br.close();                if (bw != null)                    bw.close();            } catch (IOException e) {            }        }    }