Java Program to convert string to byte

Suppose you are given a String named "str". Now, your task is to write a Java program to convert the given string to Byte.

String is a class in Java which stores sequence of characters within double quotes and Byte is a wrapper class of java.lang package which wraps value of byte datatype.

Example Scenario:

Input: String str = "65";
Output: res = 65

Using Byte.valueOf() Method

The valueOf() method of Java Byte class is used to convert given string into its corresponding Byte object. It accepts a single numeric string as a parameter value and returns it as a Byte object.

Example

The following Java program shows how to convert a given String into Byte.

public class Demo {
   public static void main(String[] args) {
      String str = "65";
      System.out.println("Given String is: " + str);
      // checking type before converting 
      System.out.println("Type before converting: " + ((Object)str).getClass().getSimpleName());
      // converting to byte using Byte.valueOf()
      byte res = Byte.valueOf(str);
      System.out.println("String after converting to Byte: " + res);
      // checking type after converting 
      System.out.println("Type after converting: " + ((Object)res).getClass().getSimpleName());
   }
}

On running, this code generates following result ?

Given String is: 65
Type before converting: String
String after converting to Byte: 65
Type after converting: Byte

Using Byte.parseByte() Method

The parseByte() method of Java Byte class parses the specified string argument as a signed decimal byte.

Example

In this Java program, we are passing a signed numeric string and converting it into byte using parseByte() method.

public class Demo {
   public static void main(String[] args) {
      String str = "-127";
      System.out.println("Given String is: " + str);
      // checking type before converting 
      System.out.println("Type before converting: " + ((Object)str).getClass().getSimpleName());
      // converting to byte using Byte.parseByte()
      byte res = Byte.parseByte(str);
      System.out.println("String after converting to Byte: " + res);
      // checking type after converting 
      System.out.println("Type after converting: " + ((Object)res).getClass().getSimpleName());
   }
}

Output of the above is obtained as ?

Given String is: -127
Type before converting: String
String after converting to Byte: -127
Type after converting: Byte

Handling Errors while Converting String to Byte

Both Byte.parseByte() and Byte.valueOf() methods expects a string that represents a value within the range of byte data type, i.e. a number between -128 and 127. Therefore, you need to pass numeric string within its range otherwise you may encounter NumberFormatException.

Example

Now, let's see the practical demonstration ?

public class Demo {
   public static void main(String[] args) {
      // string value is greater than Byte range 
      String str = "130";
      System.out.println("Given String is: " + str);
      // converting to byte
      byte res = Byte.valueOf(str);
      System.out.println("String after converting toByte: " + res);
   }
}

When you execute this code, it will give following error message ?

Given String is: 130
Exception in thread "main" java.lang.NumberFormatException: Value out of range. Value:"130" Radix:10
	at java.base/java.lang.Byte.parseByte(Byte.java:195)
	at java.base/java.lang.Byte.valueOf(Byte.java:249)
	at java.base/java.lang.Byte.valueOf(Byte.java:275)
	at Demo.main(Demo.java:7)