Need help in resolving Java String issues

Question

I am developing a programmable calculator in android.I am getting user input in the form of charsequence which i then convert into string. But before i can put them in the stack i must check whether the input is an integer or a sign.

I am basically from a C++ background. So i am having issues finding the right functions to do the job. Any help would be appreciated.

Answer 1

Two possible solutions:

1. You can create a regex that checks if your string is a number
2. You can try to extract its integer value using Integer.valueOf() , and catch the exception [ NumberFormatException ] thrown - if it is not a number.

The first is most likely to be more efficient then the second

Answer 2

不允许用户在文本框（Edittext）中输入文本和特殊字符。当用户在文本框中输入数字时，将该数字转换为整数，如下所示Integer.parseInt（yourstring）;

Answer 3

You need to us Integer.parseInt and catch the appropriate NumberFormatException if the user does not enter a number:

try
{
  // the String to int conversion happens here
  int i = Integer.parseInt(s.trim());

  // print out the value after the conversion
  System.out.println("int i = " + i);
}
catch (NumberFormatException nfe)
{
  System.out.println("NumberFormatException: " + nfe.getMessage());
}

Answer 4

通过[+ - ]？\\ d *可以匹配此正则表达式的输入验证