Java Integer parseInt() method

The parseInt() method of Java Integer class parses the CharSequence argument as a signed decimal integer. The second parameter parses the string argument as a signed integer in the radix specified by the second argument. The third parameter parses the CharSequence argument as a signed int in the specified radix, beginning at the specified beginIndex and extending to endIndex -1. Syntax

1. public static int parseInt(String s) throws NumberFormatException
2. public static int parseInt(String s, int radix) throws NumberFormatException
3. public static int parseInt(CharSequence s, int beginIndex, int endIndex, int radix) throws NumberFormatException

Parameters s- a String containing the int representation to be parsed. radix- the radix to be used while parsing s. beginIndex- the beginning index. endIndex- the ending index.  Return Value This method returns an integer value represented by the argument in decimal or by the subsequence in the specified radix. Throws This method throws: NumberFormatException- if the String does not contain a parsable int. IndexOutOfBoundsException- if beginIndex is negative, or if beginIndex is greater than endIndex or if endIndex is greater than s.length(). NumberFormatException- if the CharSequence does not contain a parsable int in the specified radix, or if radix is either smaller than Character.MAX_RADIX or larger than Character.MAX_RADIX.  Example 1

public class JavaIntegerParseIntExample1 {
    public static void main(String[] args) {
        String s="123";
        //parses the CharSequence argument as a signed decimal integer
        int val=Integer.parseInt(s);
        System.out.println(val);
    }
}

Output

123

Example 2

public class JavaIntegerParseIntExample2 {
    public static void main(String[] args) {
        String s="123";
        int radix=9;
        //parses the string argument as a signed integer in the radix specified by the second argument
        int val=Integer.parseInt(s,radix);
        System.out.println(val);
    }
}

Output

102

Example 3

public class JavaIntegerParseIntExample3 {
    public static void main(String[] args) {
        String s="123";
        //radix should be smaller than Character.MAX_RADIX i.e. 36 else it will give you an error
        int radix=37;
        //parses the string argument as a signed integer in the radix specified by the second argument
        int val=Integer.parseInt(s,radix);
        System.out.println(val);
    }
}

Output

Exception in thread "main" java.lang.NumberFormatException: radix 37 greater than Character.MAX_RADIX

              at java.lang.Integer.parseInt(Integer.java:551)

              at com.TutorialAndExample.JavaIntegerParseIntExample3.main(JavaIntegerParseIntExample3.java:9)

Example 4

public class JavaIntegerParseIntExample4 {
    public static void main(String[] args) {
        //give NumberFormatException if the String does not contain a parsable int
        String s=null;
        //radix should be smaller than Character.MAX_RADIX i.e. 36 else it will give you an error
        int radix=37;
       /*It parses the CharSequence argument as a signed as a signed int in the specified radix,
        beginning at the specified beginIndex and extending to endIndex -1.*/
        int val=Integer.parseInt(s,radix);
        System.out.println(val);
    }
}

Output

Exception in thread "main" java.lang.NumberFormatException: null

              at java.lang.Integer.parseInt(Integer.java:542)

              at com.TutorialAndExample.JavaIntegerParseIntExample4.main(JavaIntegerParseIntExample4.java:10)