Different ways for String to Integer Conversions in Java

Given a String in Java, the task is to convert this String into Integer.

Examples:

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:

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   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);     } }

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   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:

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

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   Output:

   Integer using valueOf() = 1234
   

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