How to Convert a String to an Int in Java

1. Convert a String to an int Using parseInt() in Java
2. Convert String to an int Using Apache in Java
3. Convert String to an int Using decode() in Java
4. Convert String to an int Using valueOf() in Java
5. Convert String to an int Using parseUnsignedInt() in Java
6. Convert String After Removing Non-Numeric Chars Using replaceAll() in Java

This tutorial introduces how to convert a String to an int in Java and lists some example codes to understand it.

Convert a String to an int Using parseInt() in Java

Both String and int are data types in Java. The String is used to store textual information while int is used to store numerical data.

Here, we use the parseInt() method of the Integer class that returns an integer. Since Java does implicit auto-boxing, then we can store it into int primitive type. See the example below.

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1234";
    int int_val = Integer.parseInt(str);
    System.out.println(int_val);
  }
}

Output:

1234

Convert String to an int Using Apache in Java

If you are working with the Apache library, you can use the toInt() method of NumberUtils class that returns an int value. If the passed string contains any non-numeric char, this method does not throw any exception, but returns 0. It is safe to use toInt() rather than parseInt() which throws NumberFormatException. See the example below.

import org.apache.commons.lang3.math.NumberUtils;

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1234";
    int int_val = NumberUtils.toInt(str);
    System.out.println(int_val);
    str = "1234x"; // non-numeric string
    int_val = NumberUtils.toInt(str);
    System.out.println(int_val);
  }
}

Output:

1234
0

Convert String to an int Using decode() in Java

We can use the decode() method of the Integer class to get int value from a string. It returns Integer value, but if you want to get int (primitive) value then use intValue() with decode() method. See the example below.

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1424";
    int int_val = Integer.decode(str);
    System.out.println(int_val);
    // int primitive
    int_val = Integer.decode(str).intValue();
    System.out.println(int_val);
  }
}

Output:

1424
1424

Convert String to an int Using valueOf() in Java

We can use the valueOf() method to get an int value of a string after conversion.

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1424";
    int int_val = Integer.valueOf(str);
    System.out.println(int_val);
  }
}

1424
1424

Convert String to an int Using parseUnsignedInt() in Java

If we want to convert a string that does not include a sign, use the parseUnsignedInt() method to get int value. It works fine with unsigned string value and throws an exception if the value is signed.

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1424";
    int int_val = Integer.parseUnsignedInt(str);
    System.out.println(int_val);
  }
}

Output:

1424

Convert String After Removing Non-Numeric Chars Using replaceAll() in Java

If the string contains non-numeric chars, use the replaceAll() method of String class with regex to remove all the non-numeric chars and then use the parseInt() method of Integer class to get its equivalent integer value. See the example below.

public class SimpleTesting {
  public static void main(String[] args) {
    String str = "1424x";
    str = str.replaceAll("[^\\d]", "");
    int int_val = Integer.parseInt(str);
    System.out.println(int_val);
  }
}

Output:

1424