Java With Us

The <code>byte</code> Primitive in Java — 8-bit Signed Integer

Updated on 2026-04-21 Reviewed by the Java With Us editorial team

byte is an 8-bit signed two's-complement integer ranging from -128 to 127. You almost never declare a single byte — you use byte[] for binary data: files, network packets, hashes, image buffers.

Why signed bytes hurt

byte b = (byte) 200;      // cast needed — 200 overflows byte
System.out.println(b);    // -56, because 200 wraps to -56

int unsigned = b & 0xFF;  // 200 — classic trick to read as unsigned
int unsigned2 = Byte.toUnsignedInt(b);  // 200 — Java 8+, clearer

byte[] for binary data

byte[] bytes = Files.readAllBytes(path);
byte[] hash  = MessageDigest.getInstance("SHA-256").digest(input);
byte[] enc   = Base64.getDecoder().decode("SGVsbG8=");  // "Hello"

// Convert between byte[] and String — ALWAYS specify a charset
String s = new String(bytes, StandardCharsets.UTF_8);
byte[] b = "hello".getBytes(StandardCharsets.UTF_8);

Hex formatting

// Java 17+
HexFormat.of().formatHex(hash);         // "a591a6d40bf420..."

// Older
StringBuilder sb = new StringBuilder();
for (byte b : hash) sb.append(String.format("%02x", b));

Common mistakes

  • Reading a byte as unsigned by accident — byte b = (byte) 0xFF; int i = b; gives -1, not 255. Use b & 0xFF.
  • Missing charset on getBytes()/new String(bytes) — uses the platform default, which varies. Always pass a charset.
  • Using byte for small positive counters — no memory win versus int, and you lose the top half of the range. Just use int.

Related

Pillar: Java primitives. Tool: Base64 Encoder/Decoder. See also char.

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