StringBytes

com.ajaxjs.util.StringBytes converts text and bytes. Choose the constructor matching the direction: String for getBytes(Charset) / getUTF8_Bytes(), and byte[] for getString(Charset) / getUTF8_String().

The no-argument getBytes() / getString() and null charset use the platform default, reported by showPlatformDefaultCharset(). Prefer an explicit charset in protocols and files.

Hexadecimal

bytesToHex(byte[]) returns uppercase hex. hexToBytes(String) accepts upper/lowercase hex, returns empty bytes for empty input, and rejects odd length or non-hex characters with IllegalArgumentException. Null hex inputs are rejected.

import com.ajaxjs.util.StringBytes;
import com.ajaxjs.util.ObjectHelper;

byte[] utf8 = new StringBytes("你好").getUTF8_Bytes();
String text = new StringBytes(utf8).getUTF8_String();
String hex = StringBytes.bytesToHex(new byte[]{0x1A, 0x2B}); // 1A2B
byte[] restored = StringBytes.hexToBytes(hex);
byte[] combined = ObjectHelper.concat(restored, new byte[]{0x3C});

Byte concatenation belongs to ObjectHelper.concat(byte[], byte[]). These conversions do not detect encodings or validate application data.