Convert String, byte array

Strings are composed of characters, and characters of bytes. Chars use 2 bytes each, but often with ASCII text they can be represented in 1 byte.

With the String constructor, we create a String based on the elements in a byte array. And with String's getBytes methods, we convert String data to byte arrays.

Byte array, String

This program creates a byte array with the values 97, 98 and 99. These numbers are ASCII codes for the lowercase letters "abc."

public class Program {
    public static void main(String[] args) {

        // These are the ASCII values for lowercase A, B and C.
        byte[] array = { 97, 98, 99 };
        String result = new String(array);
        System.out.println(result);
    }
}
abc

String, byte array

Excellent support too exists for converting a String to a byte array. We use getBytes, a method on the String class.

import java.io.UnsupportedEncodingException;
import java.util.Arrays;

public class Program {
    public static void main(String[] args) throws UnsupportedEncodingException {

        // The string we want to convert.
        String letters = "abc";
        System.out.println(letters);

        // Use default charset.
        byte[] valuesDefault = letters.getBytes();
        // ... Use Arrays.toString to display our byte array.
        System.out.println(Arrays.toString(valuesDefault));

        // Specify US-ASCII char set directly.
        byte[] valuesAscii = letters.getBytes("US-ASCII");
        System.out.println(Arrays.toString(valuesAscii));
    }
}
abc
[97, 98, 99]
[97, 98, 99]

Charsets are complex

Not all text is easy-to-process 7-bit ASCII. With byte arrays, we convert 2 byte chars into 1 byte elements. This is problematic but sometimes safe.

In Java, built-in approaches, like the String constructor and the getBytes methods, are handy. We can specify charsets. And for debugging, Arrays.toString displays byte arrays.