Java中InputStream重复使用问题的几种解决方案

import java.io.*;

public class InputStreamReuser {
    public static void main(String[] args) throws IOException {
        String data = "Hello World";
        InputStream inputStream = new ByteArrayInputStream(data.getBytes());
        
        // 第一次读取前标记
        if (inputStream.markSupported()) {
            inputStream.mark(0); // 参数是readlimit，0表示不限制
        }
        
        // 第一次读取
        System.out.println("第一次读取:");
        readAndPrint(inputStream);
        
        // 重置流
        if (inputStream.markSupported()) {
            inputStream.reset();
        }
        
        // 第二次读取
        System.out.println("第二次读取:");
        readAndPrint(inputStream);
    }
    
    private static void readAndPrint(InputStream is) throws IOException {
        int content;
        while ((content = is.read()) != -1) {
            System.out.print((char) content);
        }
        System.out.println();
    }
}

import java.io.*;

public class InputStreamCacher {
    public static void main(String[] args) throws IOException {
        InputStream originalStream = new FileInputStream("example.txt");
        
        // 将流内容缓存到字节数组
        byte[] bytes = readAllBytes(originalStream);
        originalStream.close();
        
        // 创建可重复使用的流
        InputStream reusableStream1 = new ByteArrayInputStream(bytes);
        InputStream reusableStream2 = new ByteArrayInputStream(bytes);
        
        // 使用流1
        System.out.println("第一次使用:");
        readAndPrint(reusableStream1);
        
        // 使用流2
        System.out.println("第二次使用:");
        readAndPrint(reusableStream2);
    }
    
    private static byte[] readAllBytes(InputStream is) throws IOException {
        ByteArrayOutputStream buffer = new ByteArrayOutputStream();
        byte[] data = new byte[1024];
        int nRead;
        while ((nRead = is.read(data, 0, data.length)) != -1) {
            buffer.write(data, 0, nRead);
        }
        return buffer.toByteArray();
    }
    
    private static void readAndPrint(InputStream is) throws IOException {
        int content;
        while ((content = is.read()) != -1) {
            System.out.print((char) content);
        }
        System.out.println();
    }
}

import org.apache.commons.io.IOUtils;
import java.io.*;

public class CommonsIOExample {
    public static void main(String[] args) throws IOException {
        InputStream originalStream = new FileInputStream("example.txt");
        
        // 将流转换为字节数组
        byte[] bytes = IOUtils.toByteArray(originalStream);
        originalStream.close();
        
        // 创建可重复使用的流
        InputStream reusableStream1 = new ByteArrayInputStream(bytes);
        InputStream reusableStream2 = new ByteArrayInputStream(bytes);
        
        // 使用流
        System.out.println("第一次使用: " + IOUtils.toString(reusableStream1, "UTF-8"));
        System.out.println("第二次使用: " + IOUtils.toString(reusableStream2, "UTF-8"));
    }
}

import java.io.*;

public class ResettableInputStream extends InputStream {
    private final InputStream original;
    private InputStream current;
    private byte[] buffer;
    private boolean buffered = false;
    
    public ResettableInputStream(InputStream original) {
        this.original = original;
        this.current = original;
    }
    
    @Override
    public int read() throws IOException {
        return current.read();
    }
    
    public void resetStream() throws IOException {
        if (!buffered) {
            // 第一次重置时缓存内容
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            byte[] data = new byte[1024];
            int nRead;
            while ((nRead = original.read(data, 0, data.length)) != -1) {
                baos.write(data, 0, nRead);
            }
            buffer = baos.toByteArray();
            buffered = true;
        }
        current = new ByteArrayInputStream(buffer);
    }
    
    @Override
    public void close() throws IOException {
        original.close();
        if (buffered && current != null) {
            current.close();
        }
    }
}

// 使用示例
public class Main {
    public static void main(String[] args) throws IOException {
        ResettableInputStream ris = new ResettableInputStream(new FileInputStream("example.txt"));
        
        // 第一次读取
        System.out.println("第一次读取:");
        readAndPrint(ris);
        
        // 重置
        ris.resetStream();
        
        // 第二次读取
        System.out.println("第二次读取:");
        readAndPrint(ris);
        
        ris.close();
    }
    
    private static void readAndPrint(InputStream is) throws IOException {
        int content;
        while ((content = is.read()) != -1) {
            System.out.print((char) content);
        }
        System.out.println();
    }
}