1.1.字节流复制文件

//运用字节输入输出流将a.txt文件复制到b.txt中
public class Demo1 {public static void main(String[] args) throws IOException {//创建输入流对象FileInputStream fis = new FileInputStream("day11_myIO\\a.txt");//可以使用BufferedInputStream的子类对象进行包装,可以提高读取数据的效率(底存为数组)BufferedInputStream bis = new BufferedInputStream(fis);//创建输出流对象FileOutputStream fos = new FileOutputStream("day11_myIO\\b.txt");//可以使用BufferedOutputStream的子类对象进行包装,可以提高读取数据的效率(底存为数组)BufferedOutputStream bos = new BufferedOutputStream(fos);//读取a.txtbyte[] bytes = new byte[1024];int len =bis.read(bytes);//记录读取字节的个数while (len!=-1){//一边读取,一边写入bos.write(bytes,0,len);//System.out.println(len);//写完再读len =bis.read();}//释放资源bos.close();bis.close();}
}

1.2.字节流捕获异常

//字节流输出写入扑获异常
public class Demo2 {public static void main(String[] args) {FileOutputStream fos = null;try {//创建流对象fos = new FileOutputStream("day11_myIO\\a.txt");//写数据fos.write("hello".getBytes());} catch (IOException e) {e.printStackTrace();//如果异常，则抛出打印到控制台} finally {//不管异常是否发生，finally里面的代码一定会执行（释放资源的代码）if (fos != null) {//如果创建对象失败，则会为nulltry {         //判断是否为空，避免空指针异常//释放资源fos.close();} catch (IOException e) {e.printStackTrace();}}}}
}

1.3.字节输入流读取数据并打印至控制台

//字节流InPutStream为字节流读数据抽象类
//具体使用它的子类FileInputStream【输入流】
public class Demo1 {public static void main(String[] args) throws IOException {//构造方法，参数为File对象//FileInputStream fs = new FileInputStream(new File("day11_myIO\\a.txt"));//构造方法，参数为文件路径//1.创建输入流FileInputStream fis = new FileInputStream("day11_myIoByteStream\\a.txt");//2.一次读一个字节/*int b = fis.read(); // 返回的则为字节对应的值while (b!=-1){System.out.print((char)b);b = fs.read();a.txt}*///一次读多个字节byte[] bytes = new byte[1024];int len = fis.read(bytes);while (len!=-1){//返回-1则读完String str = new String(bytes, 0, len);System.out.println(str);len = fis.read(bytes);}//3.释放资源(关流)fis.close();}
}
打印结果：
------------------------------------------------------------------------------
hello
world
java

2.1.字符流复制文件

//BufferedReader,BufferedWriter字符缓冲输入输出流
//特有方法:bw.newLine();换行符[跨平台性];br.readLine();读取一行数据
public class Demo1 {public static void main(String[] args) throws IOException {//1.创建对象//创建BufferedReader对象对FileReader进行包装BufferedReader br = new BufferedReader(new FileReader("day12_myIoCharStream\\a.txt"));//创建BufferedWriter对象对FileWriter进行包装BufferedWriter bw = new BufferedWriter(new FileWriter("day12_myIoCharStream\\b.txt"));//2.读数据String line = br.readLine();//读取到返回一行的字符串while (line!=null){//line为读到的每一行数据//边读边写bw.write(line);bw.newLine();bw.flush();line = br.readLine();}bw.close();br.close();}
}

2.2.字符流读取文本学生信息，操作后再写入文本

public class Demo2 {public static void main(String[] args) throws IOException {//1.读取//创建字符输入流对象BufferedReader br = new BufferedReader(new FileReader("day12_myIoCharStream\\c.txt"));//2.字符缓冲输入流读取文本ArrayList<Student> list = new ArrayList<Student>();String line = br.readLine();while (line!=null){//3.将读取的信息切割封装为学生对象存入集合中String[] strArr = line.split(",");list.add(new Student(strArr[0],Integer.parseInt(strArr[1])));line = br.readLine();}//循环结束,数据全部存入集合,释放资源br.close();//4.将集合安装学生年龄排序Collections.sort(list,(o1, o2) -> o1.getAge()-o2.getAge());//System.out.println(list);//5.排序完毕,创建字符输出流写入文本BufferedWriter bw = new BufferedWriter(new FileWriter("day12_myIoCharStream\\d.txt"));//6.遍历集合,得到每一个学生对象,写入文本for (Student student : list) {StringBuilder sb = new StringBuilder();bw.write(sb.append(student.getName()).append(",").append(student.getAge()).toString());//bw.write(student.getName()+","+student.getAge());bw.newLine();bw.flush();}bw.close();}
}

2.3.字符串解码

//字符串解编码
public class Demo1 {public static void main(String[] args) throws UnsupportedEncodingException {//编码:把字符串转化为字节数组[一个汉字UTF-8默认三个字节,GBK中是二个字节]byte[] byte1 = "你好世界".getBytes("gbk");System.out.println(Arrays.toString(byte1));//解码//解码使用的编码表必须和编码保持一致//通过使用平台的默认字符集解码指定的字节数组来构造新的StringString s1 = new String(byte1);//由于idea默认为utf-8，则打印出来乱码//通过指定的字符集解码指定的字节数组来构造新的StringString s2 = new String(byte1, "gbk");System.out.println(s1);System.out.println(s2);}
}打印结果：
-------------------------------------------------------------------------------
[-60, -29, -70, -61, -54, -64, -67, -25]
�������
你好世界