Different ways for String to Integer Conversions in Java - GeeksforGeeks

29 May, 2019
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

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 lengthThe value represented by the string is not a value of type intSpecifically 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_RADIXAny 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 1Example: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
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: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

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 lengthThe value represented by the string is not a value of type intSpecifically 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_RADIXAny 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 1Example: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

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_RADIXAny 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
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:
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);    }}
Integer using first variant of praseInt = 1234
Integer using second (radix) variant of praseInt = 4660

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: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

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

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