I/O

Modern HTTP client

Old URL url = new URL("https://api.com/data"); HttpURLConnection con = (HttpURLConnection) url.openConnection(); con.setRequestMethod("GET"); BufferedReader in = new BufferedReader( new InputStreamReader(con.getInputStream())); // read lines, close streams...

Modern var client = HttpClient.newHttpClient(); var request = HttpRequest.newBuilder() .uri(URI.create("https://api.com/data")) .build(); var response = client.send( request, BodyHandlers.ofString()); String body = response.body();

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JDK 11+ learn more →

I/O

WebSocket clients with java.net.http

Old WebSocketClient client = new WebSocketClient(serverUri) { @Override public void onMessage(String message) { handle(message); } }; client.connect();

Modern HttpClient.newHttpClient() .newWebSocketBuilder() .buildAsync(serverUri, new WebSocket.Listener() { @Override public CompletionStage<?> onText( WebSocket socket, CharSequence data, boolean last) { handle(data.toString()); return WebSocket.Listener.super .onText(socket, data, last); } });

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JDK 11+ learn more →

I/O

Deprecated URL constructors to URI

Old URL endpoint = new URL("https://example.com/api?q=java");

Modern URI endpointUri = URI.create("https://example.com/api?q=java"); URL endpoint = endpointUri.toURL();

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JDK 20+ learn more →

I/O

IO class for console I/O

Old import java.util.Scanner; Scanner sc = new Scanner(System.in); System.out.print("Name: "); String name = sc.nextLine(); System.out.println("Hello, " + name); sc.close();

Modern String name = IO.readln("Name: "); IO.println("Hello, " + name);

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JDK 25+ learn more →

I/O

Reading files

Old StringBuilder sb = new StringBuilder(); try (BufferedReader br = new BufferedReader( new FileReader("data.txt"))) { String line; while ((line = br.readLine()) != null) sb.append(line).append("\n"); } String content = sb.toString();

Modern String content = Files.readString(Path.of("data.txt"));

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JDK 11+ learn more →

I/O

Writing files

Old try (FileWriter fw = new FileWriter("out.txt"); BufferedWriter bw = new BufferedWriter(fw)) { bw.write(content); }

Modern Files.writeString( Path.of("out.txt"), content );

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JDK 11+ learn more →

I/O

Default-charset file I/O to explicit StandardCharsets

Old try (Reader reader = new FileReader(path.toFile())) { return readAll(reader); }

Modern try (BufferedReader reader = Files.newBufferedReader( path, StandardCharsets.UTF_8)) { return readAll(reader); }

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JDK 7+ learn more →

I/O

InputStream.transferTo()

Old byte[] buf = new byte[8192]; int n; while ((n = input.read(buf)) != -1) { output.write(buf, 0, n); }

Modern input.transferTo(output);

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JDK 9+ learn more →

I/O

Path.of() factory

Old Path path = Paths.get("src", "main", "java", "App.java");

Modern var path = Path.of("src", "main", "java", "App.java");

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JDK 11+ learn more →

I/O

Try-with-resources improvement

Old Connection conn = getConnection(); // Must re-declare in try try (Connection c = conn) { use(c); }

Modern Connection conn = getConnection(); // Use existing variable directly try (conn) { use(conn); }

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JDK 9+ learn more →

I/O

Finalizers to deterministic resource cleanup

Old @Override protected void finalize() throws Throwable { nativeHandle.release(); }

Modern final class NativeResource implements AutoCloseable { private static final Cleaner CLEANER = Cleaner.create(); private static final class State implements Runnable { private final long handle; State(long handle) { this.handle = handle; } @Override public void run() { release(handle); } } private final Cleaner.Cleanable cleanable; NativeResource(long handle) { cleanable = CLEANER.register(this, new State(handle)); } @Override public void close() { cleanable.clean(); } }

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JDK 9+ learn more →

I/O

File memory mapping

Old try (FileChannel channel = FileChannel.open(path, StandardOpenOption.READ, StandardOpenOption.WRITE)) { MappedByteBuffer buffer = channel.map( FileChannel.MapMode.READ_WRITE, 0, (int) channel.size()); // Limited to 2GB // Freed by GC, no control }

Modern FileChannel channel = FileChannel.open(path, StandardOpenOption.READ, StandardOpenOption.WRITE); try (Arena arena = Arena.ofShared()) { MemorySegment segment = channel.map( FileChannel.MapMode.READ_WRITE, 0, channel.size(), arena); // No size limit // ... } // Deterministic cleanup

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JDK 22+ learn more →

I/O

Files.mismatch()

Old // Compare two files byte by byte byte[] f1 = Files.readAllBytes(path1); byte[] f2 = Files.readAllBytes(path2); boolean equal = Arrays.equals(f1, f2); // loads both files entirely into memory

Modern long pos = Files.mismatch(path1, path2); // -1 if identical // otherwise: position of first difference

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JDK 12+ learn more →

I/O

Deserialization filters

Old // Dangerous: accepts any class ObjectInputStream ois = new ObjectInputStream(input); Object obj = ois.readObject(); // deserialization attacks possible!

Modern ObjectInputFilter filter = ObjectInputFilter.Config .createFilter( "com.myapp.*;!*" ); ois.setObjectInputFilter(filter); Object obj = ois.readObject();

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JDK 9+ learn more →