integer value of a string

Question

What function is to be used in java so as to print the integer value of a string.
Please explain, maybe with the help of an example.

Example String:

String str = new String("HELLO");

Answer 1

If you want to find say the ASCII integer representation of an entire string and print that out you could use the String.charAt(..) method.

public class test 
{
   public static void main( String argv[] )
   {
      String str = new String("HELLO");
      int age = 0; 
      for( int i = 0; i < str.length(); i++ ) {  // Loop through the string 
        age += (int) str.charAt(i);  // Add the current character's int representation to the age. 
        System.out.println( "Character: " + str.charAt(i) + " Integer value: " + (int)str.charAt(i) );
      }

      System.out.println( "Age: " + age );
   }
}

Corrisponding output:

Character: H Integer value: 72
Character: E Integer value: 69
Character: L Integer value: 76
Character: L Integer value: 76
Character: O Integer value: 79
Age: 372

Answer 2

You mean convert a String into an integer?

You can do:

int val = Integer.parseInt(str);

Answer 3

One of the two functions:

Integer.valueOf(num); //returns Integer (Object)
Integer.parseInt(num); //returns int (primitive)

are what you want. Docs: parseInt, valueOf. However, it may often throw an exception, which you may not want. I often use:

/** returns int value or null if invalid */
public static Integer intOf(String num) {
 if (num == null) return null;
 try {
  return Integer.valueOf(num);
 } catch (NumberFormatException e) {
  return null;
 }
}

Answer 4

Try

String inputStr = "the age is 44";

String patternStr = "[0-9]+"; //or "([0-9]+)" ?
// Compile and use regular expression
Pattern pattern = Pattern.compile(patternStr);
Matcher matcher = pattern.matcher(inputStr);
boolean matchFound = matcher.find();

if (matchFound) {
    // System.out.println(matcher.groupCount());
    return matcher.group(0);
} else {
    return null;
}

(from http://www.exampledepot.com/egs/java.util.regex/Group.html )