java --字节流 和 字符流的相关使用方法

//字节流: INputStream/OutputStream
//字符流: Reader/Writer

static String path = "路径";

public static void main(String[] args) throws IOException {
//        demo1();
//        demo2();
//        demo3();
//        demo4();
//        demo5();
//        demo6();
//        demo7();
//        demo8();
//        demo9();
//        demo10();
//        demo11();
//        demo12();
//        demo13();
//        demo14();
demo15();
}

/*******************************
* 字节流
******************************/

//读
public static void demo1() throws IOException {

//对文件操作的类
//参数是文件的路径
File file = new File("路径/xxx.txt");
//选择输入的字节流进行操作
FileInputStream fileInputStream = new FileInputStream(file);
//读内容
int x
4000
= fileInputStream.read();
System.out.println(x);
int y = fileInputStream.read();
System.out.println(y);
int z = fileInputStream.read();
System.out.println(z);
int t = fileInputStream.read();
System.out.println(t);
//关闭流
fileInputStream.close();
}

public static void demo2() throws IOException {
//对文件操作的类
//参数是文件的路径
File file = new File("路径/xxx.txt");
//选择输入的字节流进行操作
FileInputStream fileInputStream = new FileInputStream(file);
//读内容
int x = 0;
while ((x = fileInputStream.read()) != -1) {
System.out.println(x);
}
fileInputStream.close();
}

//写
public static void demo3() throws IOException {

File file = new File("路径/yyy.txt");
//若有文件,就覆盖内容
//若没有文件,新建文件夹并写入
//       FileOutputStream fileOutputStream = new FileOutputStream(file);
//若要追加内容,需要使用重载方法,第二个参数true
FileOutputStream fileOutputStream = new FileOutputStream(file, true);

fileOutputStream.write(100);
fileOutputStream.write(101);
fileOutputStream.write(102);

fileOutputStream.close();
}

//图片拷贝
public static void demo4() throws IOException {
FileInputStream fileInputStream = new FileInputStream(path + "1.jpg");
FileOutputStream fileOutputStream = new FileOutputStream(path + "copy_1.jpg");
int b = 0;
while ((b = fileInputStream.read()) != 0) {
fileOutputStream.write(b);
}
fileInputStream.close();
fileOutputStream.close();
}

//MP3拷贝
public static void demo5() throws IOException {

FileInputStream fileInputStream = new FileInputStream(path + "whzg.mp3");
FileOutputStream fileOutputStream = new FileOutputStream(path + "copy_whzg.mp3");
int b = 0;
while ((b = fileInputStream.read()) != 0) {
fileOutputStream.write(b);
}
fileInputStream.close();
fileOutputStream.close();
}

//大数组的方式拷贝
//弊端 - 被拷贝文件太大的时候,会造成内存溢出
public static void demo6() throws IOException {
FileInputStream fileInputStream = new FileInputStream(path + "whzg.mp3");
FileOutputStream fileOutputStream = new FileOutputStream(path + "new_whzg.mp3");
//File类中 - file.length()获取文件的长度
//fileInputStream.available();不阻塞情况下,可读取的最大长度
int len = fileInputStream.available();
System.out.println(len);
//缓存区 - 鸡蛋蓝
byte[] arr = new byte[len];

//将文件内容读到一个arr中
fileInputStream.read(arr);
//将arr中的内容写入到文件夹中
fileOutputStream.write(arr);

fileInputStream.close();
fileOutputStream.close();

}

//小数组的拷贝方式
//注意: 小心缓存数组中存储着上一次读取的部分内容
public static void demo7() throws IOException {
FileInputStream fileInputStream = new FileInputStream(path + "xxx.txt");
FileOutputStream fileOutputStream = new FileOutputStream(path + "zzz.txt");
//缓存区 - 鸡蛋蓝
byte[] arr = new byte[1024 * 8];

//        //将文件内容读到一个arr中
//        fileInputStream.read(arr);
//
//        for (int i = 0; i < arr.length; i++) {
//            System.out.println(arr[i]);
//        }
//
//        fileInputStream.read(arr);
//        for (int i = 0; i < arr.length; i++) {
//            System.out.println(arr[i]);
//        }
int len1 = 0;
//read (arr) -> 将内容读到数组中
//返回值 : 当有内容读时,返回每次实际读取到的字节数
//        当无内容课读时,返回-1
while ((len1 = fileInputStream.read(arr)) != -1) {
//将arr中的内容写入到文件中
//            fileOutputStream.write(arr);
//将参数1中的内容写入到文件中
//从数组的第参数2个的位置开始,写入参数3的长度
fileOutputStream.write(arr, 0, len1);
}
//将arr中的内容写入到文件夹中
//        fileOutputStream.write(arr);
fileInputStream.close();
fileOutputStream.close();

}

//系统自带的缓冲
public static void demo8() throws IOException {
FileInputStream fileInputStream = new FileInputStream(path + "xxx.txt");
FileOutputStream fileOutputStream = new FileOutputStream(path + "zzz.txt");
//将fileInputStream包装一下,使其带有缓存区
BufferedInputStream bis = new BufferedInputStream(fileInputStream);
//将fileOutputStream包装一下,使其带有缓存区
BufferedOutputStream bos = new BufferedOutputStream(fileOutputStream);
int b = 0;
while ((b = bis.read()) != 0) {
bos.write(b);
}
//flush 刷新
//close刷新并关闭流
//将缓存区的内容刷新进文件
//        bos.flush();
//        bos.write(100);
//        bos.flush();

//注意:不需要再关闭fileInputStream和fileOutputStream
//因为bis和bos 就是对其进行了包装
bis.close();
bos.close();

}

//字节流读取中文字符
public static void demo9() throws IOException {

FileInputStream fileInputStream = new FileInputStream(path + "xxx.txt");
//一个中文字符由2/3/n个字节组成
//因此写个缓存,一次读出对应的字节数
byte[] arr = new byte[3];
int b = 0;
while ((b = fileInputStream.read(arr)) != -1) {
//将字节还原成中文字符,再输出
System.out.print(new String(arr, 0, b));
}
fileInputStream.close();
}

//字节流写中文字符
public static void demo10() throws IOException {
FileOutputStream fos = new FileOutputStream(path + "yyy.txt");
//写入内容
fos.write("你好,你好!!!".getBytes());
//写入换行
fos.write("\r\n".getBytes());
fos.close();
}

/********************************************

c309
* 字符流
*************************************/
//读
public static void demo11() throws IOException {
File flie = new File(path + "xxx.txt");
FileReader fr = new FileReader(flie);
int c = 0;
while ((c = fr.read()) != -1) {
System.out.print((char) c);
}
fr.close();
}

//写
public static void demo12() throws IOException {

File flie = new File(path + "xxx.txt");
FileWriter fw = new FileWriter(flie);
fw.write("大家好!!");
fw.write(97);
fw.close();
}

//字符流不能拷贝非纯文本的文件,因为会将不识别的字符读成?再写到新文本中
//拷贝

//也不推荐使用字符流拷贝纯文本文件,因为读和写都需要多一步转码的过程

//只有直接读出字符内容的文档或者单纯写入时才推荐使用字符流
public static void demo13() throws IOException {

FileReader fr = new FileReader(path + "xxx.txt");
FileWriter fw = new FileWriter(path + "ccc.txt");
int c = 0;
while ((c = fr.read()) != -1) {
fw.write(c);
}
fr.close();
//注意:Writer类中有一个2k的小缓冲区,若不关流
//    会将内容写到缓冲区,关闭流后才刷新到硬盘上
fw.close();
}

//自带缓冲区的拷贝
public static void demo14() throws IOException {
FileReader fr = new FileReader(path + "xxx.txt");
FileWriter fw = new FileWriter(path + "ccc.txt");

//将fr 和 br 包装到缓冲区
BufferedReader br = new BufferedReader(fr);
BufferedWriter bw = new BufferedWriter(fw);

int c = 0;
while ((c = br.read()) != -1) {
bw.write(c);
//"\r\n"与newLine都是换行的作用
//newLine的兼容性更高,可跨平台
bw.newLine();
}
br.close();
bw.close();
}

//readline() - 按行读
public static void demo15() throws IOException {

FileReader fr = new FileReader(path + "xxx.txt");
BufferedReader br = new BufferedReader(fr);
String line = null;
while ((line = br.readLine()) != null) {
System.out.println(line);
}
br.close();
}