学习javaEE的日子 Day36 字符流-编程知识

Day36

1.字符流

应用场景：操作纯文本数据

注意：字符流 = 字节流+编译器

编译器：可以识别中文字符和非中文字符，非中文字符获取1个字节（一个字节=一个字符），编译器会根据编码格式获取中文字符对应的字节数（GBK获取两个字节，UTF-8获取三个字节）

abstract class Reader – 字符输入流的基类（抽象类）

abstract class Writer – 字符输出流的基类（抽象类）

class InputStreamReader extends Reader – 字符输入转换流

class OutputStreamWriter extends Writer – 字符输出转换流

特点：将字节流转换为字符流，字符转换流是字节流和字符流的桥梁

class FileReader extends InputStreamReader – 文件字符输入流

class FileWriter extends OutputStreamWriter – 文件字符输出流

class BufferedReader extends Reader – 带缓冲区的字符输入流

class BufferedWriter extends Writer – 带缓冲区的字符输出流

默认缓冲区：8192字符 – new char[8192]

在这里插入图片描述

1.1 利用字符输出转换流向文件写入数据OutputStreamWriter

1)不处理异常的方式

2)文件存在的情况

3)文件不存在的情况

经验：所有的输出流，文件不存在的情况都会创建文件

public class Test01 {public static void main(String[] args) throws IOException {//1.创建流对象(将文件字节输出流 转换为 字符输出转换流)OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("io.txt"));//2.写入数据//osw.write(97);//写入码值//char[] cs = {'1','2','3','a','b','c','我','爱','你'};//osw.write(cs);//写入字符数组//osw.write(cs, 3, 4);//写入字符数组，偏移量，写入长度//osw.write("123abc我爱你");//字符串osw.write("123abc我爱你", 3, 4);//写入字符串，偏移量，写入长度//3.关闭资源osw.close();}
}

文件末尾追加

经验：考虑基础流的构造方法

注意：使用字符转换流最好加上编码格式！！！！！！！

public class Test02 {public static void main(String[] args) throws IOException {//1.创建流对象(将文件字节输出流 转换为 字符输出转换流)OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("io.txt",true),"UTF-8");//2.写入数据osw.write("123abc我爱你");//3.关闭资源osw.close();		}
}

1.2 利用字符输入转换流读取文件里的数据InputStreamReader

不处理异常

文件存在

文件不存在

经验：所有的输入流，在文件不存在时都会报错

public class Test05 {public static void main(String[] args) throws IOException {//1.创建流对象InputStreamReader isr = new InputStreamReader(new FileInputStream("io.txt"));//2.读取数据//int read;//while((read = isr.read()) != -1){//	System.out.println((char)read);//}//2.读取数据//isr.read(cs)：读入cs数组长度的字符，将字符数据存入到数组中，并返回读取到的有效字节数，如果读取到文件末尾，则返回-1char[] cs = new char[1024];int len;while((len = isr.read(cs)) != -1){System.out.println(new String(cs, 0, len));}       //3.关闭资源isr.close();}
}

1.3 拷贝文件

public class Copy {public static void main(String[] args) throws UnsupportedEncodingException, IOException {InputStreamReader isr = new InputStreamReader(new FileInputStream("小说.txt"), "GBK");OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream("copy.txt"), "GBK");char[] cs = new char[1024];int len;while((len = isr.read(cs)) != -1){osw.write(cs, 0, len);}isr.close();osw.close();}
}

1.4 利用文件字符输出流向文件写入数据FileWriter

public class Test01 {public static void main(String[] args) throws IOException {//1.创建流对象//FileWriter fw = new FileWriter("io.txt");//1.创建流对象FileWriter fw = new FileWriter("io.txt", true);//2.写入数据fw.write("好好学习");//3.关闭资源fw.close();}
}

1.5 利用文件字符输入流读取文件里的数据FileReader

public class Test02 {public static void main(String[] args) throws IOException {//1.创建流对象FileReader fr = new FileReader("io.txt");//2.读取数据char[] cs = new char[1024];int len;while((len = fr.read(cs)) != -1){System.out.println(new String(cs, 0, len));}//3.关闭资源fr.close();}
}

1.6 拷贝文件

public class Copy {public static void main(String[] args) throws IOException {FileReader fr = new FileReader("小说.txt");FileWriter fw = new FileWriter("copy.txt");char[] cs = new char[1024];int len;while((len = fr.read(cs)) != -1){fw.write(cs, 0, len);}fr.close();fw.close();}
}

1.7 利用带缓冲区的字符输出流向文件写入数据BufferedWriter

public class Test01 {public static void main(String[] args) throws UnsupportedEncodingException, IOException {//1.创建流对象（文件字节输出流 -> 字符输出转换流 -> 带有缓冲区的字符输出流）//默认缓冲区大小：8192字符//BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("io.txt"), "GBK"));//1.创建流对象（文件字节输出流 -> 字符输出转换流 -> 带有缓冲区的字符输出流）+ 末尾追加//默认缓冲区大小：8192字符//BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(new FileOutputStream("io.txt",true), "GBK"));//1.创建流对象（文件字符输出流 -> 带缓冲区的字符输出流）//默认缓冲区大小：8192字符//BufferedWriter bw = new BufferedWriter(new FileWriter("io.txt"));//1.创建流对象（文件字符输出流 -> 带缓冲区的字符输出流）+ 末尾追加//默认缓冲区大小：8192字符//BufferedWriter bw = new BufferedWriter(new FileWriter("io.txt",true));//1.创建流对象（文件字符输出流 -> 带缓冲区的字符输出流）+ 末尾追加 //自定义缓冲区大小：2048字符BufferedWriter bw = new BufferedWriter(new FileWriter("io.txt",true),2048);//2.写入数据bw.write("好好学习");//3.关闭资源bw.close();		}
}

1.8 利用带有缓冲区的字符输入流读取文件里的数据BufferedReader

public class Test02 {public static void main(String[] args) throws UnsupportedEncodingException, IOException {//1.创建流对象（文件字节输入流 -> 字符输入转换流 -> 带有缓冲区的字符输入流）//默认缓冲区大小：8192字符//BufferedReader br = new BufferedReader(new InputStreamReader(new FileInputStream("io.txt"), "GBK"));//1.创建流对象（文件字节输入流 -> 字符输入转换流 -> 带有缓冲区的字符输入流）//默认缓冲区大小：8192字符//BufferedReader br = new BufferedReader(new FileReader("io.txt"));//1.创建流对象（文件字节输入流 -> 字符输入转换流 -> 带有缓冲区的字符输入流）//自定义缓冲区大小：2048字符BufferedReader br = new BufferedReader(new FileReader("io.txt"),2048);//2.读取数据char[] cs = new char[1024];int len;while((len = br.read(cs)) != -1){System.out.println(new String(cs, 0, len));}//3.关闭资源br.close();}
}

1.9 拷贝文件

public class Copy01 {public static void main(String[] args) throws IOException {BufferedReader br = new BufferedReader(new FileReader("С˵.txt"));BufferedWriter bw = new BufferedWriter(new FileWriter("copy.txt"));char[] cs = new char[1024];int len;while((len = br.read(cs)) != -1){bw.write(cs, 0, len);}br.close();bw.close();}
}

另一种方法

public class Copy02 {public static void main(String[] args) throws IOException {BufferedReader br = new BufferedReader(new FileReader("小说.txt"));BufferedWriter bw = new BufferedWriter(new FileWriter("copy.txt"));//		String readLine;
//		while((readLine = br.readLine()) != null){
//			bw.write(readLine);//写一行
//			bw.newLine();//换行
//		}boolean bool = false;String readLine;while((readLine = br.readLine()) != null){//第一行不换行if(bool){bw.newLine();//换行}bw.write(readLine);//写一行bool = true;}br.close();bw.close();}
}