To convert String to int in Java you can use one of the following options-
- Integer.parseInt(String str) method which returns the passed String as int.
- Integer.valueOf(String str) method which returns the passed String as Integer.
Java example to convert String to int using Integer.parseInt()
public class StringToInt {
public static void main(String[] args) {
String str = "12";
try{
int num = Integer.parseInt(str);
System.out.println("value - " + num);
// can be used in arithmetic operations now
System.out.println(num+"/3 = " + num/3);
}catch(NumberFormatException exp){
System.out.println("Error in conversion " + exp.getMessage());
}
}
}
Output
value - 12 12/3 = 4
Java example to convert String to int using Integer.valueOf
public class StringToInt {
public static void main(String[] args) {
String str = "12";
try{
Integer num = Integer.valueOf(str);
System.out.println("value - " + num);
// can be used in arithmetic operations now
System.out.println(num+"/3 = " + num/3);
}catch(NumberFormatException exp){
System.out.println("Error in conversion " + exp.getMessage());
}
}
}
Output
value - 12 12/3 = 4
In this example you can see that valueOf() method returns Integer object, because of autoboxing it can directly be used as int value though.
NumberFormatException
In the examples you can see a try-catch block which catches NumberFormatException which is thrown if an invalid number string is passed for converting to int.
public class StringToInt {
public static void main(String[] args) {
String str = "123ab";
try{
Integer num = Integer.valueOf(str);
System.out.println("value - " + num);
// can be used in arithmetic operations now
System.out.println(num+"/3 = " + num/3);
}catch(NumberFormatException exp){
System.out.println("Error in conversion " + exp.getMessage());
throw exp;
}
}
}
Output
Error in conversion For input string: "123ab" Exception in thread "main" java.lang.NumberFormatException: For input string: "123ab" at java.lang.NumberFormatException.forInputString(Unknown Source) at java.lang.Integer.parseInt(Unknown Source) at java.lang.Integer.valueOf(Unknown Source) at com.knpcode.programs.StringToInt.main(StringToInt.java:8)
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