Java中字符流

输入字符流

字节流读取文件

package com.cloud.reader; import java.io.File; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.util.Arrays; public class Demo4 {    public static void main(String[] args) throws IOException {       readTest();    }    //字节流读取文件    public static void readTest() throws IOException{       File file = new File("F:\\a.txt");       FileInputStream fileInputStream = new FileInputStream(file);       byte[] buf = new byte[1024];       for(int i=0;i<3;i++){         fileInputStream.read(buf);         System.out.println(new String(buf));       }       fileInputStream.close();    }    //使用字节流写中文    public static void writeTest() throws IOException{       File file = new File("F:\\a.txt");       FileOutputStream fileOutputStream = new FileOutputStream(file);       String data="大家好";       byte[] buf = data.getBytes();       System.out.println("输出内容："+Arrays.toString(buf));       fileOutputStream.write(buf);       fileOutputStream.close();    } }

字符输入流流程

package com.cloud.reader; import java.io.File; import java.io.FileReader; import java.io.IOException; /* 字节流：字节流读取的是文件中的二进制数据，不会自动转为可以看懂的字符 字符流：把读到的数据进行对应的编码与解码。字符流=字节流+编码（解码） 输入字符流： --|Reader 输入字符流的基类  抽象类 ----|FileReader 读取文件的输入字符流  */ public class Demo5 {    public static void main(String[] args) throws IOException {       readTest2();    }    //缓冲字符数据读取文件    public static void readTest2() throws IOException{       File file = new File("F:\\a.txt");       FileReader fileReader = new FileReader(file);       char[] buf = new char[1024];       int length = 0;       while((length = fileReader.read(buf))!=-1){         System.out.println(new String(buf,0,length));       }       fileReader.close();    }    //字符流读取文件    public static void readTest1() throws IOException{       File file = new File("F:\\a.txt");       FileReader fileReader = new FileReader(file);       int content = 0;       while((content = fileReader.read())!=-1){         System.out.println((char)content);       }       fileReader.close();    } }

输出字符流

输出字符流流程

package com.cloud.reader; import java.io.File; import java.io.FileWriter; import java.io.IOException; public class Demo6 {    public static void main(String[] args) throws IOException {       File file = new File("F:\\a.txt");       FileWriter fileWriter = new FileWriter(file);       String data = "今天天气真好";       fileWriter.write(data);       fileWriter.close();    } }

 

缓冲输入字符流

缓冲输入字符流流程

package com.cloud.reader; import java.io.BufferedReader; import java.io.File; import java.io.FileReader; import java.io.IOException; import java.util.Arrays;   /* 输入字符流 --|Reader 所有输入字符流的基类，抽象类 ----|FileReader 读取文件字符串的输入字符流 ----|BufferReader 缓冲输入字符流，提高读取文件的效率，拓展FileReader的功能，内部维护字符数组 注：缓冲流不具备读写文件的能力  */ public class Demo1 {    public static void main(String[] args) throws IOException {       File file = new File("F:\\a.txt");       FileReader fileReader = new FileReader(file);       String line = null;       while((line = myReadLine(fileReader))!=null){         System.out.println(line);       }    }    //自己实现ReadLine方法    public static String myReadLine(FileReader fileReader) throws IOException{       //创建一个字符串缓冲对象       StringBuilder sb = new StringBuilder();//用来存储读取的数据       int content = 0;       while((content=fileReader.read())!=-1){         if(content=='\r'){            continue;         }         else if(content=='\n'){            break;         }else{            sb.append((char)content);         }       }       //数据读完       if(content==-1){         return null;       }       return sb.toString();    }    public static void readTest() throws IOException{       //找到目标文件       File file = new File("F\\a.txt");       //建立数据的输入通道       FileReader fileReader = new FileReader(file);       //建立缓冲输入字符流       BufferedReader bufferedReader = new BufferedReader(fileReader);       //读取数据       String line = null;       while((line = bufferedReader.readLine())!=null){          System.out.println(Arrays.toString("aaa".getBytes()));       }       bufferedReader.close();    } }

缓冲输出字符流

缓冲输出字符流流程

package com.cloud.reader; import java.io.BufferedWriter; import java.io.File; import java.io.FileWriter; import java.io.IOException; /* 输出字符流 --|Writer 所有输出字符流的基类，抽象类 ----|FileWriter 向文件输出字符数据的输出字符流 ----|BufferdWriter 缓冲输出字符流，内部维护长度为8192的字符数据作为缓冲区  */ public class Demo2 {    public static void main(String[] args) throws IOException{       File file = new File("F:\\a.txt");       FileWriter fileWriter = new FileWriter(file);       BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);       bufferedWriter.write("\r\n");       bufferedWriter.write("Hello,EveryOne");       bufferedWriter.flush();    } }

字符流案例

登陆案例

package com.cloud.reader;   import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.File; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.Scanner;   public class Demo3 {    static Scanner scanner = new Scanner(System.in);    public static void main(String[] args) throws IOException {       System.out.println("选择功能：A：注册，B：登陆");       String option = scanner.next();       if("a".equalsIgnoreCase(option)){         //注册         reg();       }       else if("b".equalsIgnoreCase(option)){         //登陆         login();       }       else{         System.out.println("输入错误...");       }    }    //登陆    @SuppressWarnings("resource")    public static void login() throws IOException{       System.out.println("请输入用户名...");       String userName = scanner.next();       System.out.println("请输入密码...");       String password = scanner.next();       String info = userName+""+password;       BufferedReader bufferedReader = new BufferedReader(new FileReader("F:\\a.txt"));       String line = null;       boolean isLogin = false;       while((line = bufferedReader.readLine())!=null){         if(info.equals(line)){            isLogin = true;            break;         }       }       if(isLogin){         System.out.println("欢迎"+userName+"登陆成功");       }else{         System.out.println("不存在该用户请注册");       }    }    //注册    public static void reg() throws IOException{       System.out.println("请输入用户名：");       String userName = scanner.next();       System.out.println("请输入密码：");       String password = scanner.next();       String info = userName+""+password;       File file = new File("F:\\a.txt");       FileWriter fileWriter = new FileWriter(file);       BufferedWriter bufferedWriter = new BufferedWriter(fileWriter);       bufferedWriter.write(info);       bufferedWriter.newLine();       bufferedWriter.close();    } }

字符流拷贝文件

package com.cloud.reader; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; public class Demo7 {    public static void main(String[] args) throws IOException {       // 字符流拷贝文件       BufferedReader bufferedReader = new BufferedReader(new FileReader("F:\\a.txt"));       BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter("F:\\b.txt"));       String line = null;       while ((line = bufferedReader.readLine())!=null) {         bufferedWriter.write(line);       }       bufferedWriter.close();       bufferedReader.close();    } }