I/O & File Operations

/**
 * Stream copying and conversion utilities
 */
public abstract class StreamUtils {
    public static final int BUFFER_SIZE = 4096;
    
    // Stream to byte array/string conversion
    public static byte[] copyToByteArray(InputStream in) throws IOException;
    public static String copyToString(InputStream in, Charset charset) throws IOException;
    public static String copyToString(ByteArrayOutputStream baos, Charset charset);
    
    // Copy operations
    public static void copy(byte[] in, OutputStream out) throws IOException;
    public static void copy(String in, Charset charset, OutputStream out) throws IOException;
    public static int copy(InputStream in, OutputStream out) throws IOException;
    public static long copyRange(InputStream in, OutputStream out, long start, long end) throws IOException;
    
    // Stream utilities
    public static int drain(InputStream in) throws IOException;
    public static InputStream emptyInput();
    public static InputStream nonClosing(InputStream in);
    public static OutputStream nonClosing(OutputStream out);
}

/**
 * NIO file operations, zip handling, and byte conversions
 */
public class NioUtils {
    // Zip operations
    public static void unzip(String zipFilename, String destDirname) throws IOException;
    public static void create(String zipFilename, String... filenames) throws IOException;
    public static void list(String zipFilename) throws IOException;
    
    // File operations
    public static void deleteOldFiles(String dirPath, int olderThanMinute);
    public static String getFileExtension(File file);
    public static String getFileExtension(String name);
    
    // ByteBuffer operations
    public static ByteBuffer toByteBuffer(String s);
    public static ByteBuffer toByteBuffer(File file) throws IOException;
    
    // System utilities
    public static String getTempDir();
    
    // Conversion utilities
    public static byte[] toByteArray(InputStream is) throws IOException;
    public static String toString(InputStream is) throws IOException;
}

import com.networknt.utility.StreamUtils;
import com.networknt.utility.NioUtils;

// Stream operations
InputStream input = new FileInputStream("data.txt");
byte[] data = StreamUtils.copyToByteArray(input);
String content = StreamUtils.copyToString(input, StandardCharsets.UTF_8);

// Copy between streams
InputStream source = new FileInputStream("source.txt");
OutputStream dest = new FileOutputStream("dest.txt");
int bytesCopied = StreamUtils.copy(source, dest);

// Zip operations
NioUtils.create("archive.zip", "file1.txt", "file2.txt");
NioUtils.unzip("archive.zip", "/extracted/");
NioUtils.list("archive.zip");

// File utilities
String extension = NioUtils.getFileExtension("document.pdf"); // "pdf"
String tempDir = NioUtils.getTempDir();
NioUtils.deleteOldFiles("/logs", 60); // Delete files older than 60 minutes

// ByteBuffer operations
ByteBuffer buffer = NioUtils.toByteBuffer("Hello World");
ByteBuffer fileBuffer = NioUtils.toByteBuffer(new File("data.bin"));