Java 字节流操作文件：读取、写入和复制示例

import java.io.*;

public class InputDemo {

public static void main(String[] args) throws IOException {
    String str1, str2, str3;

    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    System.out.println('请输入第一个字符串：');
    str1 = br.readLine();

    System.out.println('请输入第二个字符串：');
    str2 = br.readLine();

    System.out.println('请输入第三个字符串：');
    str3 = br.readLine();

    // 拼接字符串
    StringBuffer sb = new StringBuffer();
    sb.append(str1).append(str2).append(str3);
    String content = sb.toString();

    // 写入文件
    FileOutputStream fos = new FileOutputStream('c:\inputDemo.txt');
    fos.write(content.getBytes());

    // 读取文件
    FileInputStream fis = new FileInputStream('c:\inputDemo.txt');
    int len = 0;
    byte[] buffer = new byte[1024];
    while ((len = fis.read(buffer)) != -1) {
        System.out.print(new String(buffer, 0, len));
    }

    // 复制文件
    FileInputStream fis2 = new FileInputStream('c:\inputDemo.txt');
    FileOutputStream fos2 = new FileOutputStream('c:\inputDemo2.txt');
    len = 0;
    while ((len = fis2.read(buffer)) != -1) {
        fos2.write(buffer, 0, len);
    }

    fos.close();
    fis.close();
    fis2.close();
    fos2.close();
}

}