Different ways for String to Integer Conversions in Java

Input: str = "1234"
Output: 1234

Input: str = "456"
Output: 456

1. Convert using Integer.parseInt(String) The Integer class has a static method that returns an integer object representing the specified String parameter. Syntax :

   public static int parseInt(String str) throws NumberFormatException
   or
   public static int parseInt(String str, int radix) throws NumberFormatException
   

   Parameters:
   • str: A string which needs to be converted to the integer. It can also have the first character as a minus sign ‘-‘ (‘\u002D’) or plus sign ‘+’ (‘\u002B’) to represent the sign of the number.
   • radix: The radix used while the string is being parsed. This parameter is only specific to the second variant of the method.
   Exceptions: NumberFormatException is thrown by this method if any of the following situations occurs: For both the variants:
   • String is null or of zero length
   • The value represented by the string is not a value of type int
   • Specifically for the parseInt(String s, int radix) variant of the function:
     • The second argument radix is either smaller than Character.MIN_RADIX or larger than Character.MAX_RADIX
     • Any character of the string is not a digit of the specified radix, except that the first character may be a minus sign '-' ('\u002D') or plus sign '+' ('\u002B') provided that the string is longer than length 1
   Example: JAVA

   class GfG {
       public static void main(String args[])
       {
           String str = "1234";
   
           int num1 = Integer.parseInt(str);
           System.out.println("Integer using "
                              + "first variant of"
                              + " praseInt = "
                              + num1);
   
           int num2 = Integer.parseInt(str, 16);
           System.out.println("Integer using "
                              + "second (radix) variant"
                              + " of praseInt = "
                              + num2);
       }
   }
   

   Output:

   Integer using first variant of praseInt = 1234
   Integer using second (radix) variant of praseInt = 4660
   

2. Convert using Integer.valueOf(String) Syntax:

   public static Integer valueOf(String str)
   

   Parameters: This method accepts single parameter str of String type that is to be parsed. Return Value: The method returns an Integer object holding the value represented by the string argument. Example: JAVA

   class GfG {
       public static void main(String args[])
       {
           String str = "1234";
   
           int num1 = Integer.valueOf(str);
           System.out.println("Integer using"
                              + " valueOf() = "
                              + num1);
       }
   }
   

   Output:

   Integer using valueOf() = 1234