Charset
- Java course
- Expert
- Lesson 16/46
- 5 min
Learn byte-character conversion with Charset.
Encoding with Charset
A Charset converts between strings and bytes. NIO provides this in the java.nio.charset package. The StandardCharsets class keeps common sets ready, such as UTF-8, UTF-16, and ISO-8859-1.
Example: "AB".getBytes(StandardCharsets.UTF_8) turns the string into UTF-8 bytes. UTF-8 is ASCII compatible, so 'A' and 'B' are one byte each. Non-ASCII letters take two bytes. Without the right set, strings look broken; so always state the encoding explicitly.
Encoding and decoding
Turning a string into bytes is called encoding; turning bytes into a string is decoding. NIO does this through a Charset object with encode and decode methods.
Example: Charset utf8 = StandardCharsets.UTF_8; ByteBuffer buf = utf8.encode("AB");. Here buf is a two-byte buffer. Conversely utf8.decode(buf) gives the string back. This cycle is the basis for processing bytes from files and networks as strings.
Practice Encode a string to UTF-8 bytes
Get a byte array with "AB".getBytes(StandardCharsets.UTF_8). Print the length property of the byte array with System.out.println.
Starter code
// Encode to bytes with UTF_8
// Print with lengthSample solution
import java.nio.charset.StandardCharsets;
public class CharsetDemo {
public static void main(String[] args) {
byte[] bytes = "AB".getBytes(StandardCharsets.UTF_8);
System.out.println(bytes.length);
}
}Expected output
2
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What does StandardCharsets.UTF_8 define?
- A character encoding Correct answer
- A buffer
- A channel
- A path
Explanation: UTF_8 is a character encoding.
2 Match the Charset concepts
| Term | Meaning |
|---|---|
StandardCharsets.UTF_8 |
Character encoding |
getBytes |
String to bytes |
Charset |
Encoding abstraction |
new String |
Bytes to string |
3 Encode with UTF_8
"AB".getBytes(StandardCharsets.____);"AB".getBytes(StandardCharsets.UTF_8);Explanation: StandardCharsets.UTF_8 is the common encoding.