Java字节流

import java.io.*;

public class ByteStreamBasics {
    
    // 演示FileInputStream读取文件
    public static void demonstrateFileInputStream(String fileName) {
        FileInputStream fis = null;
        try {
            fis = new FileInputStream(fileName);
            
            // 逐字节读取
            int byteData;
            while ((byteData = fis.read()) != -1) {
                System.out.print((char)byteData);
            }
            
        } catch (IOException e) {
            System.err.println("读取文件时发生错误: " + e.getMessage());
        } finally {
            if (fis != null) {
                try {
                    fis.close();
                } catch (IOException e) {
                    System.err.println("关闭流时发生错误: " + e.getMessage());
                }
            }
        }
    }
    
    // 演示FileOutputStream写入文件
    public static void demonstrateFileOutputStream(String fileName, String content) {
        try (FileOutputStream fos = new FileOutputStream(fileName)) {
            // 将字符串转换为字节数组并写入
            byte[] bytes = content.getBytes();
            fos.write(bytes);
            
            System.out.println("成功写入文件: " + fileName);
            
        } catch (IOException e) {
            System.err.println("写入文件时发生错误: " + e.getMessage());
        }
    }
}

// 使用普通流复制文件
private static void copyFileWithNormalStream(String sourceFile, String targetFile) {
    try (FileInputStream fis = new FileInputStream(sourceFile);
         FileOutputStream fos = new FileOutputStream(targetFile)) {
        
        int byteData;
        while ((byteData = fis.read()) != -1) {
            fos.write(byteData);
        }
        
    } catch (IOException e) {
        System.err.println("普通流复制文件失败: " + e.getMessage());
    }
}

// 使用缓冲流复制文件
private static void copyFileWithBufferedStream(String sourceFile, String targetFile) {
    try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(sourceFile));
         BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(targetFile))) {
        
        int byteData;
        while ((byteData = bis.read()) != -1) {
            bos.write(byteData);
        }
        
    } catch (IOException e) {
        System.err.println("缓冲流复制文件失败: " + e.getMessage());
    }
}

// 写入不同类型的数据
public static void demonstrateDataOutput(String fileName) {
    try (DataOutputStream dos = new DataOutputStream(
            new BufferedOutputStream(new FileOutputStream(fileName)))) {
        
        // 写入不同类型的数据
        dos.writeBoolean(true);
        dos.writeByte(127);
        dos.writeShort(32767);
        dos.writeInt(2147483647);
        dos.writeLong(9223372036854775807L);
        dos.writeFloat(3.14159f);
        dos.writeDouble(2.718281828459045);
        dos.writeUTF("Hello, DataStream!");
        
        System.out.println("数据写入完成");
        
    } catch (IOException e) {
        System.err.println("写入数据时发生错误: " + e.getMessage());
    }
}

// 按写入顺序读取数据
public static void demonstrateDataInput(String fileName) {
    try (DataInputStream dis = new DataInputStream(
            new BufferedInputStream(new FileInputStream(fileName)))) {
        
        boolean boolValue = dis.readBoolean();
        byte byteValue = dis.readByte();
        short shortValue = dis.readShort();
        int intValue = dis.readInt();
        long longValue = dis.readLong();
        float floatValue = dis.readFloat();
        double doubleValue = dis.readDouble();
        String stringValue = dis.readUTF();
        
        // 输出读取的数据
        System.out.println("boolean: " + boolValue);
        System.out.println("byte: " + byteValue);
        System.out.println("short: " + shortValue);
        System.out.println("int: " + intValue);
        System.out.println("long: " + longValue);
        System.out.println("float: " + floatValue);
        System.out.println("double: " + doubleValue);
        System.out.println("String: " + stringValue);
        
    } catch (IOException e) {
        System.err.println("读取数据时发生错误: " + e.getMessage());
    }
}

// 演示ByteArrayOutputStream的使用
public static void demonstrateByteArrayOutput() {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    
    try {
        // 写入字符串数据
        String text1 = "Hello, ";
        String text2 = "ByteArrayStream!";
        
        baos.write(text1.getBytes());
        baos.write(text2.getBytes());
        
        // 获取字节数组
        byte[] data = baos.toByteArray();
        
        System.out.println("写入的数据: " + new String(data));
        System.out.println("字节数组长度: " + data.length);
        System.out.println("流的大小: " + baos.size());
        
        // 重置流
        baos.reset();
        System.out.println("重置后流的大小: " + baos.size());
        
    } catch (IOException e) {
        System.err.println("操作ByteArrayOutputStream时发生错误: " + e.getMessage());
    } finally {
        try {
            baos.close();
        } catch (IOException e) {
            System.err.println("关闭流时发生错误: " + e.getMessage());
        }
    }
}

// 演示ByteArrayInputStream的使用
public static void demonstrateByteArrayInput() {
    String originalText = "Java字节数组流示例";
    byte[] data = originalText.getBytes();
    
    ByteArrayInputStream bais = new ByteArrayInputStream(data);
    
    try {
        System.out.println("原始数据: " + originalText);
        System.out.println("可用字节数: " + bais.available());
        
        // 批量读取
        byte[] buffer = new byte[1024];
        int bytesRead = bais.read(buffer);
        if (bytesRead != -1) {
            String readText = new String(buffer, 0, bytesRead);
            System.out.println("读取的内容: " + readText);
        }
        
    } catch (IOException e) {
        System.err.println("操作ByteArrayInputStream时发生错误: " + e.getMessage());
    } finally {
        try {
            bais.close();
        } catch (IOException e) {
            System.err.println("关闭流时发生错误: " + e.getMessage());
        }
    }
}