java String！= null无法从bufferedReader读取

Question

In android I am getting the String value from BufferedReader and it is null after reading from file.

intstring = br.readLine();
System.out.println(intstring);
if(intstring != null)
{
      System.out.println("Inside if condition");
      int istring = Integer.parseInt(intstring);
}

My output is

 null
 Inside if condition
 NumberFormatException

Help me please

Answer 1

Your NumberFormatException is happening because your input isn't a number. Maybe it's a blank line, or maybe it has some non-numeric characters. In fact, your output suggests that it's actually the word "null" .

You've got some options.

• You could check that the string contains digits and no other characters before you parse it, for example by using a regular expression and a condition like if (intString.matches("\\\\d+")) .
• You could catch the NumberFormatException , and do something particular when it happens.
• You could check whether your string is blank, if you knew that there weren't going to be any non-numeric characters in the input. For this option, you might write if (!intString.equals(""))) .