FileReader的編碼問題

有一個UTF-8編碼的文本文件，用FileReader讀取到一個字符串，然后轉換字符集：str=new String(str.getBytes(),"UTF-8");結果大部分中文顯示正常，但最后仍有部分漢字顯示為問號！

public static List<String> getLines( String fileName )
{
    List<String> lines = new ArrayList<String>();
    try
    {
        BufferedReader br = new BufferedReader(new FileReader(fileName));
        String line = null;
        while( ( line = br.readLine() ) != null )
            lines.add(new String(line.getBytes("GBK"), "UTF-8"));
        br.close();
    }
    catch( FileNotFoundException e )
    {
    }
    catch( IOException e )
    {
    }
    return lines;
}

public static List<String> getLines( String fileName ) { List<String> lines = new ArrayList<String>(); try { BufferedReader br = new BufferedReader(new FileReader(fileName)); String line = null; while( ( line = br.readLine() ) != null ) lines.add(new String(line.getBytes("GBK"), "UTF-8")); br.close(); } catch( FileNotFoundException e ) { } catch( IOException e ) { } return lines; }

文件讀入時是按OS的默認字符集即GBK解碼的，我先用默認字符集GBK編碼str.getBytes(“GBK”)，此時應該還原為文件中的字節序列了，然后再按UTF-8解碼，生成的字符串按理說應該就應該是正確的。

 

為什么結果中還是有部分亂碼呢？
問題出在FileReader讀取文件的過程中，FileReader繼承了InputStreamReader，但並沒有實現父類中帶字符集參數的構造函數，所以FileReader只能按系統默認的字符集來解碼，然后在UTF-8 -> GBK -> UTF-8的過程中編碼出現損失，造成結果不能還原最初的字符。

原因明確了，用InputStreamReader代替FileReader，InputStreamReader isr=new InputStreamReader(new FileInputStream(fileName),"UTF-8");這樣讀取文件就會直接用UTF-8解碼，不用再做編碼轉換。

public static List<String> getLines( String fileName )
{
    List<String> lines = new ArrayList<String>();
    try
    {
        BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(fileName), "UTF-8"));
        String line = null;
        while( ( line = br.readLine() ) != null )
            lines.add(line);
        br.close();
    }
    catch( FileNotFoundException e )
    {
    }
    catch( IOException e )
    {
    }
    return lines;
}

public static List<String> getLines( String fileName ) { List<String> lines = new ArrayList<String>(); try { BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream(fileName), "UTF-8")); String line = null; while( ( line = br.readLine() ) != null ) lines.add(line); br.close(); } catch( FileNotFoundException e ) { } catch( IOException e ) { } return lines; }