How to Convert String to int in Java

You can use Integer.parseInt() or Integer.valueOf() functions to convert String to int value. In case String is not a convertible then NumberFormatException will occur.

#1. Using Integer.parseInt()

Integer.parseInt() converts string value and returns an int primitive as result. For below example, first we store 5 as string value to id variable. Then convert it to integer and save to result variable.

Save the above content in ConvsertStringToInt1.java file and compile and run this program.

[[email protected] ~]$ javac ConvertStringToInt1.java

[[email protected] ~]$ java ConvertStringToInt1

5

#2. Using Integer.valueOf()

Integer.valueOf() also uses Integer.parseInt function in backend but in result, it provides and Integer object value.

Save the above content in ConvsertStringToInt2.java file and compile and run this program.

[[email protected] ~]$ javac ConvertStringToInt2.java

[[email protected] ~]$ java ConvertStringToInt2

5

#3. Exception in Conversion

If the given input is not parsable by the any of above methods, NumberFormatException will be thrown. As in below example, we are storing string”5abc” in id variable which contains alphabets. If we try to convert this number to int, NumberFormatException exception will occur.

Save the above content in ConvsertStringToInt3.java file and compile and run this program.

[[email protected] ~]$ javac ConvertStringToInt3.java

[[email protected] ~]$ java ConvertStringToInt3

java.lang.NumberFormatException: For input string: "5abc"

Reference:

http://docs.oracle.com/javase/8/docs/api/java/lang/Integer.html