字符流
字符流呈现起因
一个汉字如果是GBK编码，占用2字节，如果是UTF-8编码，占用3个字节
编码表
字符集
采纳什么规定编码，就得采纳对应规定解码，否则就会呈现乱码
字符串中的编码解码问题
//定义一个字符串String s = "中国";//byte[] getBytes();应用平台默认字符集将该String编码为一系列字节，将后果存储到新的字节数组中byte[] bys = s.getBytes();sout(Arrays.toString(bys));//输入-28 -72 -83 -27 -101 -67//byte[] getBytes(String charsetName); 应用指定的字符集将该String编码为一系列字节，将后果存储到新的字节数组中byte[] bys = s.getBytes(charsetName:"UTF-8");sout(Arrays.toString(bys));//输入-28 -72 -83 -27 -101 -67byte[] bys = s.getBytes(charsetName:"GBK");sout(Arrays.toString(bys));//输入-42 -48 -71 -6//解码 //String(byte[] bytes) 通过平台的默认字符集解码指定的字节数组来构建新的StringString ss = new String(bys);sout(ss);//String(byte[] bytes,String charsetName) 通过指定的字符集将该String编码为一系列字节，将后果存储到新的字节数组中String ss = new String(bys,charsetName:"UTF-8");sout(ss);String ss = new String(bys,charsetName:"GBK");sout(ss);字符流中的编码解码问题
能够指定字符集
OutputStreamWriter 字符到字节，应用指定的编码将写入的字符编码为字节，应用的字符集能够由名称指定，也能够被明确指定，或者应用默认的
FileOutputStream fos = new FileOutputStream(name:"myCharStream\osw.txt");OutputStreamWriter osw = new OutputStreamWriter(fos);//简化一下OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(name:"myCharStream\osw.txt"));//默认编码OutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(name:"myCharStream\osw.txt",charsetName:"UTF-8"));//指定编码osw.write(str:"中国");osw.close();//字节解码为字符InputStreamReader isr = new InputStreamReader(new FileInputStream(name:"myCharStream\osw.txt"));//默认编码InputStreamReader isr = new InputStreamReader(new FileInputStream(name:"myCharStream\osw.txt",charsetName:"UTF-8"));//指定编码//一次读取一个字符数据int ch;while((ch = isr.read()) != -1){ System.out.print((char)by);}isr.close();字符流写数据的5种形式
//创立一个应用默认字符编码的OutputStreamWriterOutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(name:"myCharStream\osw.txt"));//void write(int c) **写一个字符**osw.write(c:97);//字符流写数据不能间接写到文件里去，当初还在缓冲区//void flush() 刷新流osw.flush();//刷新一下数据就到文件里去了 要想写进去就得刷新//void write(char[] cbuf) **写一个字符数组**char[] chs = {'a','b','c','d','e'};osw.write(chs);//void write(char[] cbuf,int off,int len) **写一个字符数组的一部分**osw.write(chs,off:0,chs.length);osw.write(chs,off:1,len:3);//从1索引开始写三个 就是bcd//void write(String str) **写一个字符串**osw.write(str:"abcde");//void write(String str,int off,int len) **写一个字符串的一部分**osw.write(str:"abcde",off:0,chs.length);osw.write(str:"abcde",off:1,len:3);//从1索引开始写三个 就是bcdosw.close();//敞开流会先刷新一下flush刷新后还能写，close敞开前会刷新然而敞开了就不能写数据了
字符流读数据的2种形式
InputStreamReader isr = new InputStreamReader(new FileInputStream(name:"myCharStream\osw.txt"));//默认编码//int read():一次读一个字符数据int ch;while((ch = isr.read()) != -1){ System.out.print((char)by);}//int read(char[] cubf):一次读一个字符数组数据char[] chs = new char[1024];int len;while((len = isr.read(chs)) != -1){ System.out.print(new String(chs,offset:0,len));}isr.close();//敞开流会先刷新一下字节流和字符流读数据的形式是一样的
复制java文件
把模块目录下的"ConversionStreamDemo.java"复制到模块目录下的"Copy.java"
//数据源创立字符输出流对象InputStreamReader isr = new InputStreamReader(new FileInputStream(name:"myCharStream\\ConversionStreamDemo.java"));//默认编码//目的地创立字符输入流对象OutputStreamWriterOutputStreamWriter osw = new OutputStreamWriter(new FileOutputStream(name:"myCharStream\\Copy.java"));//读写数据复制文件//一次读写一个字符数据int ch;while((ch = isr.read()) != -1){ osw.write(ch);}//一次读写一个字符数组数据char[] chs = new char[1024];int len;while((len = isr.read(chs)) != -1){ osw.write(chs,off:0,len);}//开释资源osw.close();isr.close();复制java文件改进版
把模块目录下的"ConversionStreamDemo.java"复制到模块目录下的"Copy.java"
//数据源创立字符输出流对象FileReader fr = new FileReader(fileName:"myCharStream\\ConversionStreamDemo.java");//目的地创立字符输入流对象FileWriter fw = new FileWriter(fileName:"myCharStream\\Copy.java");//读写数据复制文件//一次读写一个字符数据int ch;while((ch = fr.read()) != -1){ fw.write(ch);}//一次读写一个字符数组数据char[] chs = new char[1024];int len;while((len = fr.read(chs)) != -1){ fw.write(chs,off:0,len);}//开释资源fw.close();fr.close();字符缓冲流
从字符输出流中读取文本，缓冲字符，能够指定缓冲区大小，或者应用默认大小
//BufferedWriter(Writer out)FileWriter fw = new FileWriter(fileName:"myCharStream\\bw.txt");BufferedWriter bw = new BufferedWriter(fw);//综合BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\bw.txt"));//默认是8192字符的字符数组bw.write(str:"hello\r\n");bw.write(str:"world\r\n");bw.close();BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\bw.txt"));//一次读一个字符int ch;while((ch = br.read()) != -1){ System.out.print((char)ch);}//一次读取一个字符数组char[] chs = new char[1024];int len;while((len = br.read(chs)) != -1){ System.out.print(new String(chs,offset:0,len));}复制java文件 字符缓冲流改进版
把模块目录下的"ConversionStreamDemo.java"复制到模块目录下的"Copy.java"
//数据源创立字符输出流对象BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\ConversionStreamDemo.java"));//目的地创立字符输入流对象BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\Copy.java"));//读写数据复制文件//一次读写一个字符数据int ch;while((ch = br.read()) != -1){ bw.write(ch);}//一次读写一个字符数组数据char[] chs = new char[1024];int len;while((len = br.read(chs)) != -1){ bw.write(chs,off:0,len);}//开释资源bw.close();br.close();字符缓冲流特有性能
//创立字符缓冲输入流BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\bw.txt"));//写数据for(int i = 0;i < 10;i++){ bw.write(str:"hello"+i); bw.write(str:"\r\n"); //或者不必下面的换行 用上面这种写法 bw.newwLine(); bw.flush();}//创立字符缓冲输出流BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\bw.txt"));//public String readline():读一行文字//第一次读取数据 达到结尾就输入nullString line = br.readLine();sout(line);//循环改良String line;while((line = br.readLine())!=null){ sout(line);//不蕴含换行符}//开释资源bw.close();复制java文件 字符缓冲流特有性能改进版
//数据源创立字符输出流对象BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\ConversionStreamDemo.java"));//目的地创立字符输入流对象BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\Copy.java"));//读写数据复制文件//应用字符缓冲流特有性能实现String line;while((line = br.readLine())!=null){ bw.write(line);//不蕴含换行符 所有数据都在同一行 bw.newwLine(); bw.flush();}//开释资源bw.close();br.close();IO流小结
案例 汇合到文件
//创立ArrayList汇合ArrayList<String> array = new ArrayList<String>();//往汇合中存储字符串元素array.add("Hello");array.add("World");array.add("Java");//目的地创立字符缓冲输入流对象BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\array.txt"));//遍历汇合，失去每一个字符串数据for(String s ；array){ //调用字符缓冲输入流对象的办法写数据 bw.write(s);//不蕴含换行符 所有数据都在同一行 bw.newwLine(); bw.flush();}//开释资源bw.close();案例 文件到汇合
//数据源创立字符缓冲输出流对象BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\array.txt"));//创立ArrayList汇合对象ArrayList<String> array = new ArrayList<String>();//调用字符缓冲输出流对象的办法读数据String line;while((line = br.readLine())!=null){ array.add(line);}//开释资源br.close();//遍历汇合for(String s ；array){ sout(s);}案例 点名器
//数据源创立字符缓冲输出流对象BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\name.txt"));//创立ArrayList汇合对象ArrayList<String> array = new ArrayList<String>();//调用字符缓冲输出流对象的办法读数据String line;while((line = br.readLine())!=null){ //把读取到的数据存储到汇合中 array.add(line);}//开释资源br.close();//应用Random产生一个随机数，随机数的范畴在0-汇合长度Random r = new Random();int index = r.nextInt(array.size());//把下面产生的随机数作为索引到汇合中获取值String name = array.get(index);//输入sout(name);案例 汇合到文件改进版
//创立ArrayList汇合ArrayList<Student> array = new ArrayList<Student>();//创立学生对象Student s1 = new Student(sid:"itheima001",name:"林青霞",age:"30",address:"西安");Student s2 = new Student(sid:"itheima002",name:"张曼玉",age:"35",address:"武汉");Student s3 = new Student(sid:"itheima003",name:"王祖贤",age:"33",address:"郑州");//把学生对象增加到汇合中array.add(s1);array.add(s2);array.add(s3);//目的地创立字符缓冲输入流对象BufferedWriter bw = new BufferedWriter(new FileWriter(fileName:"myCharStream\\Student.txt"));//遍历汇合，失去每一个学生对象for(Student s ；array){ //把学生对象的数据拼接成指定格局的字符串 StringBuilder sb = new StringBuilder(); sb.append(s.getSid()).append(",").append(s.getName()).append(",").append(s.getAge()).append(",").append(s.getAddress()); //调用字符缓冲输入流对象的办法写数据 bw.write(sb.toString());//不蕴含换行符 所有数据都在同一行 bw.newwLine(); bw.flush();}//开释资源bw.close();案例 文件到汇合改进版
//数据源创立字符缓冲输出流对象BufferedReader br = new BufferedReader(new FileReader(fileName:"myCharStream\\Student.txt"));//创立ArrayList汇合对象ArrayList<Student> array = new ArrayList<Student>();//调用字符缓冲输出流对象的办法读数据String line;while((line = br.readLine())!=null){ //把读到的字符串数据用split()进行宰割，失去一个字符串数组 String[] strArray = line.split(reqex:","); //创立学生对象 Student s = new Student(); s.setSid(strArray[0]); s.setName(strArray[1]); s.setAge(Integer.parseInt(strArray[2])); s.setAddress(strArray[3]); //把学生对象增加到汇合中 array.add(s);}//开释资源br.close();//遍历汇合for(Student s ；array){ sout(s.getSid()+","+s.getName()+","++s.getAge()+","+s.getAddress());}