java 28 lines · 6 steps

Compressing byte arrays with GZIP in Java

A small utility that round-trips byte arrays through GZIP streams using try-with-resources for safe flushing.

Explained by highlit
Intermediate compression streams try-with-resources byte-arrays
1import java.io.ByteArrayInputStream;
2import java.io.ByteArrayOutputStream;
3import java.io.IOException;
4import java.util.zip.GZIPInputStream;
5import java.util.zip.GZIPOutputStream;
6 
7public final class GzipCodec {
8 
9 public static byte[] compress(byte[] data) throws IOException {
10 ByteArrayOutputStream buffer = new ByteArrayOutputStream(Math.max(64, data.length / 2));
11 try (GZIPOutputStream gzip = new GZIPOutputStream(buffer)) {
12 gzip.write(data);
13 }
14 return buffer.toByteArray();
15 }
16 
17 public static byte[] decompress(byte[] compressed) throws IOException {
18 ByteArrayOutputStream buffer = new ByteArrayOutputStream(compressed.length * 2);
19 try (GZIPInputStream gzip = new GZIPInputStream(new ByteArrayInputStream(compressed))) {
20 byte[] chunk = new byte[8192];
21 int read;
22 while ((read = gzip.read(chunk)) != -1) {
23 buffer.write(chunk, 0, read);
24 }
25 }
26 return buffer.toByteArray();
27 }
28}
01 / 01
STEP 01

Walkthrough

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Three takeaways
  1. 1Wrapping a GZIPOutputStream in try-with-resources guarantees the trailer is written when the block closes.
  2. 2In-memory streams let you convert compression stream APIs into simple byte-array-in, byte-array-out functions.
  3. 3Reading through a fixed buffer in a loop handles output of unknown size without allocating for the whole result up front.

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