如何从文件中读取数据

public void readDate(String fileName)
  { 
    try 
      { 
        BufferedReader  in=new  BufferedReader(new  FileReader(fileName); 
        String temp=""; 
        String  s=new  String(); 
        while((s=in.readLine())!=null) 
        temp+=s+"\n"; 
        in.close();//关闭输入流 
        System.out.println(temp); 
        } 
        catch(FileNotFoundException e) 
          { 
            e.printStackTrace(); 
            } 
        catch(IOException e) 
          { 
          e.printStackTrace(); 
          } 
}

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import java.io.*; 
class E{   
public static void main(String  args[]) 
    { 
      int b; byte buffer[]=new byte[2500]; 
      try{ 
          FileInputStream readfile=new FileInputStream("E.java"); 
          b=readfile.read(buffer,0,2500); 
          try{
              String str=new String(buffer,0,b,"Default"); 
              System.out.println(str); 
              }catch(UnsupportedEncodingException e)                   
                  { 
                    System.out.println("the encoding was not found:"+e); 
                    } 
        }catch(IOException e) 
              {
              System.out.println("File read Error ！"); 
              } 
      } 
  }