JAVA 點check input係唔係integer?

Method 1: use regular expression

import java.util.regex.*;
Pattern integerPattern = Pattern.compile("^\d*$");
Matcher matchesInteger = integerPattern.matcher(myString);
boolean isInteger = matchesInteger.matches();

or
boolean isInteger = Pattern.matches("^\d*$", myString);

Methid 2: Integer.parseInt() method
praseInt() will convert string to integer

int i;
bool isNumeric = false;
try
{
i = Integer.parseInt(myString);
isNumeric = true;
// did not throw error, myString is numeric
}
catch(NumberFormatException eX)
{
// threw an error, myString is not a number
isNumeric = false;
}

try {

int i = Integer.parseInt(args[0].trim()); //成功convert 左o既話就會直接store左i 度

}
catch(NumberFormatException e) {
e.printStackTrace();
}