字符流

字符流

字符流的父类(抽象类)：

Reader：字符输入流

1.public int read() {}

2.public int read (char[] c) {}

3.public int read(char[] b, int off, int len) {}

Writer：字符输出流

1.public void write(int n) {}

2.public void write(String str) {}

3.public void write(char[] с) {}

文件字符流

FileReader：

public int read(char[] c)  //从流中读取多个字符，将读到内容存入c数组， 返回实际读到的字符数；如果达到文件的尾部，则返回-1

eg : 

public class Demo02 {
    public static void main(String[] args) throws Exception {
        //1.创建FileReader 文件字符流
        FileReader fr = new FileReader("g:\\hello.txt");
        //2.读取
        //2.1单个字符流
        //int data = 0;
        //while((data = fr.read())!=-1){//读取一个字符
        //    System.out.print((char)data);
        //}
        //2.2
        char[] buf = new char[2];
        int count = 0;
        while((count = fr.read(buf))!=-1){
            System.out.println(new String(buf,0,count));
        }
        //3.关闭
        fr.close();
    }
}

FileWriter：

public void write(String str)  //一次写多个字符，将b数组中所有字符，写入输出流

eg : 

public class Demo03 {
    public static void main(String[] args) throws IOException {
        //1.创建FileWriter对象
        FileWriter fw = new FileWriter("g:\\write.txt");
        //2.写入
        for (int i = 0; i < 10; i++) {
            fw.write("Java是世界上最好的语言\r\n");//  \r\n  换行
            fw.flush();
        }
        //3.关闭
        fw.close();
        System.out.println("执行完毕");
    }
}

public class Demo04 {
    public static void main(String[] args) throws Exception {
        //1.创建FileReader FileWriter
        FileReader fr = new FileReader("g:\\write.txt");
        FileWriter fw = new FileWriter("g:\\write2.txt");
        //2.读写
        int data = 0;
        while((data = fr.read())!=-1){
            fw.write(data);
            fw.flush();
        }
        //3.关闭
        fr.close();
        fw.close();
        System.out.println("复制完毕");
    }
}

字符缓冲流

缓冲流：BufferedReader/BufferedWriter

高效读写

支持输入换行符

可一次写一行、读一行

eg : 

public class Demo05 {
    public static void main(String[] args) throws Exception {
        //1.创建缓冲流
        FileReader fr = new FileReader("g:\\write.txt");
        BufferedReader br = new BufferedReader(fr);
        //2.读取
        //2.1第一种方式
        /*char[] buf = new char[1024];
        int count = 0;
        while((count = br.read(buf))!=-1){
            System.out.println(new String(buf,0,count));
        }*/
        //2.2第二种方式。一行一行的读取
        String line = null;
        while((line=br.readLine())!=null){
            System.out.println(line);
        }
        //3.关闭
        br.close();
    }
}

public class Demo06 {
    public static void main(String[] args) throws Exception {
        //1.创建BufferedWriter对象
        FileWriter fw = new FileWriter("g:\\buffer1.txt");
        BufferedWriter bw = new BufferedWriter(fw);
        //2.写入
        for (int i = 0; i < 10; i++) {
            bw.write("好好学习，天天向上");
            bw.newLine();//写入一个换行符windows \r\n  linux \n
            bw.flush();
        }
        //3.关闭
        bw.close();
        System.out.println("执行完毕");
    }
}