Convert String to int

Converting a String to an int or Integer is a very common operation in Java. There are a few simple ways to do this conversion. The frequently used method is Integer.parseInt() .

Integer.parseInt() method

Integer.parseInt() Parses the string argument as a signed decimal integer and throws a NumberFormatException if the string can’t be converted to an int type.

String strNum="999"; int numStr = Integer.parseInt(strNum);

The value of numStr would be 999.

If the first character is a minus(-) sign it will return a minus value.

String strNum="-999"; int numStr = Integer.parseInt(strNum);

The value of numStr would be -999.

If the given String is not valid, conversion will throws a NumberFormatException .

String strNum="asdf"; int numStr = Integer.parseInt(strNum);

The above code will throws a NumberFormatException.

Example

class TestClass{ public static void main (String[] args){ String strNum="999"; int numStr = Integer.parseInt(strNum); System.out.println("Output is " + numStr); String strNum1="-999"; int numStr1 = Integer.parseInt(strNum1); System.out.println("Output is " + numStr1); } }

Output

Value is 999 Value is -999

Integer.valueOf()

Java Integer.valueOf() returns an Integer instance representing the specified int value.

class TestClass{ public static void main (String[] args){ String strNum="999"; Integer numStr = Integer.valueOf(strNum); System.out.println("Value is " + numStr); } }

Output

Value is 999

Integer's Constructor

You can convert a string to an integer value using Integer's Constructor.

class TestClass{ public static void main (String[] args){ String strNum="999"; Integer numStr = new Integer(strNum); System.out.println("Value is " + numStr); } }

Output

Value is 999

Difference between parseInt() and valueOf()

Integer.valueOf() returns an Integer object, while Integer.parseInt() returns an int primitive.

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