How to convert a String to an int in Java
In this section, we will show you how to convert a String to an int in Java.
Input: str = "3456"
Output: 3456
Input: str = "a3456e"
Output: 0
Input: str = "-3456"
Output: 3456
Input: str = "3456"
Output: 3456
Input: str = "a3456e"
Output: 0
Input: str = "-3456"
Output: 3456
Following ways can be used for converting String to int:
1. By using Integer.parseInt() method
2. By using NumberUtils.toInt method of Apache Commons library
3. By using Ints::tryParse method of Guava library
Example 1: Use Integer.parseInt() method
Integer.parseInt() method parses the String argument as a signed decimal integer object. The characters in the string must be decimal digits, except that the first character of the string may be an ASCII minus sign '-' to indicate a negative value or an ASCII plus '+' sign to indicate a positive value. It returns the integer value which is represented by the argument in a decimal integer.
public class Main {
// Driver code
public static void main(String[] args)
{
//Example 1
String str1 = "3456";
int value1 = convertToInt(str1);
System.out.println("Integer value = " + value1);
System.out.println();
//Example 2
String str2 = "a3456e";
int value2 = convertToInt(str2);
System.out.println("Integer value = " + value2);
System.out.println();
//Example 3
String str3 = "-3456";
int value3 = convertToInt(str3);
System.out.println("Integer value = " + value3);
System.out.println();
//Example 4
String str4 = "+3456";
int value4 = convertToInt(str4);
System.out.println("Integer value = " + value4);
}
// Method to convert String to int
public static int convertToInt(String str)
{
int value = 0;
System.out.println("String = " + str);
// Convert the String
try {
value = Integer.parseInt(str);
}
catch (NumberFormatException e) {
/* This is thrown when the String
contains characters other than digits
*/
System.out.println("Invalid String");
}
return value;
}
}
Console Output:
String = 3456 Integer value = 3456 String = a3456e Invalid String Integer value = 0 String = -3456 Integer value = -3456 String = +3456 Integer value = 3456
Example 2: Use NumberUtils.toInt method of Apache Commons library
Download Apache Commons library:
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.12.0</version>
</dependency>
Another method to convert String to int is to use NumberUtils.toInt() method of Apache Commons library. If the string is an invalid number format, then 0 is always returned.
import org.apache.commons.lang3.math.NumberUtils;
public class Main {
// Driver code
public static void main(String[] args)
{
//Example 1
String str1 = "3456";
int value1 = convertToInt(str1);
System.out.println("Integer value = " + value1);
System.out.println();
//Example 2
String str2 = "a3456e";
int value2 = convertToInt(str2);
System.out.println("Integer value = " + value2);
System.out.println();
//Example 3
String str3 = "-3456";
int value3 = convertToInt(str3);
System.out.println("Integer value = " + value3);
}
// Method to convert String to int
public static int convertToInt(String str)
{
int value = 0;
System.out.println("String = " + str);
// Convert the String
value = NumberUtils.toInt(str);
return value;
}
}
import org.apache.commons.lang3.math.NumberUtils;
public class Main {
// Driver code
public static void main(String[] args)
{
//Example 1
String str1 = "3456";
int value1 = convertToInt(str1);
System.out.println("Integer value = " + value1);
System.out.println();
//Example 2
String str2 = "a3456e";
int value2 = convertToInt(str2);
System.out.println("Integer value = " + value2);
System.out.println();
//Example 3
String str3 = "-3456";
int value3 = convertToInt(str3);
System.out.println("Integer value = " + value3);
}
// Method to convert String to int
public static int convertToInt(String str)
{
int value = 0;
System.out.println("String = " + str);
// Convert the String
value = NumberUtils.toInt(str);
return value;
}
}
Console Output:
String = 3456 Integer value = 3456 String = a3456e Integer value = 0 String = -3456 Integer value = -3456
Example 3: Use Ints::tryParse method of Guava library
Download Guava library:
<dependency>
<groupId>com.google.guava</groupId>
<artifactId>guava</artifactId>
<version>31.1-jre</version>
</dependency>
Another method to convert String to integer is to use Ints::tryParse method of Guava library.
import com.google.common.primitives.Ints;
import java.util.Optional;
public class Main {
// Driver code
public static void main(String[] args)
{
//Example 1
String str1 = "3456";
int value1 = convertToInt(str1);
System.out.println("Integer value = " + value1);
System.out.println();
//Example 2
String str2 = "a3456e";
int value2 = convertToInt(str2);
System.out.println("Integer value = " + value2);
System.out.println();
//Example 3
String str3 = "-3456";
int value3 = convertToInt(str3);
System.out.println("Integer value = " + value3);
}
// Method to convert String to int
public static int convertToInt(String str)
{
int value = 0;
System.out.println("String = " + str);
// Convert the String
value = Optional.ofNullable(str)
.map(Ints::tryParse)
.orElse(0);
return value;
}
}
Console Output:String = 3456
Integer value = 3456
String = a3456e
Integer value = 0
String = -3456
Integer value = -3456
String = 3456
Integer value = 3456
String = a3456e
Integer value = 0
String = -3456
Integer value = -3456
