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# I/O & File Operations
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Stream processing, NIO operations, file handling, and byte conversions. Includes zip file handling, stream copying, and ByteBuffer operations for efficient I/O operations in microservices environments.
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## Capabilities
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### Stream Utilities
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Abstract utility class providing stream copying and conversion utilities with optimized buffer management.
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```java { .api }
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/**
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 * Stream copying and conversion utilities
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 */
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public abstract class StreamUtils {
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    public static final int BUFFER_SIZE = 4096;
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    // Stream to byte array/string conversion
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    public static byte[] copyToByteArray(InputStream in) throws IOException;
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    public static String copyToString(InputStream in, Charset charset) throws IOException;
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    public static String copyToString(ByteArrayOutputStream baos, Charset charset);
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    // Copy operations
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    public static void copy(byte[] in, OutputStream out) throws IOException;
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    public static void copy(String in, Charset charset, OutputStream out) throws IOException;
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    public static int copy(InputStream in, OutputStream out) throws IOException;
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    public static long copyRange(InputStream in, OutputStream out, long start, long end) throws IOException;
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    // Stream utilities
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    public static int drain(InputStream in) throws IOException;
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    public static InputStream emptyInput();
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    public static InputStream nonClosing(InputStream in);
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    public static OutputStream nonClosing(OutputStream out);
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}
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```
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### NIO Utilities
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NIO file operations, zip handling, and byte conversions for high-performance file processing.
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```java { .api }
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/**
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 * NIO file operations, zip handling, and byte conversions
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 */
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public class NioUtils {
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    // Zip operations
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    public static void unzip(String zipFilename, String destDirname) throws IOException;
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    public static void create(String zipFilename, String... filenames) throws IOException;
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    public static void list(String zipFilename) throws IOException;
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    // File operations
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    public static void deleteOldFiles(String dirPath, int olderThanMinute);
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    public static String getFileExtension(File file);
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    public static String getFileExtension(String name);
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    // ByteBuffer operations
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    public static ByteBuffer toByteBuffer(String s);
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    public static ByteBuffer toByteBuffer(File file) throws IOException;
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    // System utilities
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    public static String getTempDir();
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    // Conversion utilities
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    public static byte[] toByteArray(InputStream is) throws IOException;
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    public static String toString(InputStream is) throws IOException;
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}
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```
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**Usage Examples:**
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```java
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import com.networknt.utility.StreamUtils;
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import com.networknt.utility.NioUtils;
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// Stream operations
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InputStream input = new FileInputStream("data.txt");
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byte[] data = StreamUtils.copyToByteArray(input);
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String content = StreamUtils.copyToString(input, StandardCharsets.UTF_8);
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// Copy between streams
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InputStream source = new FileInputStream("source.txt");
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OutputStream dest = new FileOutputStream("dest.txt");
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int bytesCopied = StreamUtils.copy(source, dest);
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// Zip operations
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NioUtils.create("archive.zip", "file1.txt", "file2.txt");
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NioUtils.unzip("archive.zip", "/extracted/");
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NioUtils.list("archive.zip");
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// File utilities
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String extension = NioUtils.getFileExtension("document.pdf"); // "pdf"
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String tempDir = NioUtils.getTempDir();
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NioUtils.deleteOldFiles("/logs", 60); // Delete files older than 60 minutes
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// ByteBuffer operations
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ByteBuffer buffer = NioUtils.toByteBuffer("Hello World");
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ByteBuffer fileBuffer = NioUtils.toByteBuffer(new File("data.bin"));
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```