io读取文件转化为字符串

/**
    * @Author zhaihuali
    * @Description //TODO 使用FileReader读取
    * @Date 15:52 2019/10/16 0016
    * @Param [url]
    * @return java.lang.String
    **/
   public static String readString1(String url)
   {
       StringBuffer str=new StringBuffer("");
       //File file=new File();
       try {
           FileReader fr=new FileReader(url);
           int ch = 0;
           while((ch = fr.read())!=-1 )
           {
               System.out.print((char)ch+"");
               str.append((char)ch);
           }
           fr.close();
       } catch (IOException e) {
           // TODO Auto-generated catch block
           e.printStackTrace();
           System.out.println("File reader出错");

       }
       return str.toString();
   }
/**
 * @Author zhaihuali
 * @Description //TODO 按字节读取字符串 一次性全部读取完后进行转码
 * @Date 15:53 2019/10/16 0016
 * @Param [url]
 * @return java.lang.String
 **/
public static String readString2(String url) {
    String str="";
    File file = new File(url);
    try {
        FileInputStream in=new FileInputStream(file);
        // size 为字串的长度 ，这里一次性读完
        int size=in.available();
        byte[] buffer=new byte[size];
        in.read(buffer);
        in.close();
        str=new String(buffer,"UTF-8");
    } catch (IOException e) {
        e.printStackTrace();
    }
    return str;
}

/**
 * @Author zhaihuali
 * @Description //TODO 按行读对于要处理的格式化数据是一种读取的好方式
 * @Date 16:02 2019/10/16 0016
 * @Param [path]
 * @return java.lang.String
 **/
public static String readString3(String path)
{
    int len=0;
    StringBuffer str=new StringBuffer("");
    File file=new File(path);
    try {
        FileInputStream is=new FileInputStream(file);
        InputStreamReader isr= new InputStreamReader(is);
        BufferedReader in= new BufferedReader(isr);
        String line=null;
        while( (line=in.readLine())!=null )
        {
            if(len != 0) // 处理换行符的问题
            {
                str.append("\r\n"+line);
            }
            else
            {
                str.append(line);
            }
            len++;
        }
        in.close();
        is.close();
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    return str.toString();
}