Java IO流--使用FileReader字符输入流读入数据到java程序或者内存的基本操作

二、流的体系结构
抽象基类         节点流（或文件流）                               缓冲流（处理流的一种）
InputStream     FileInputStream   (read(byte[] buffer))        BufferedInputStream (read(byte[] buffer))
OutputStream    FileOutputStream  (write(byte[] buffer,0,len)  BufferedOutputStream (write(byte[] buffer,0,len) / flush()
Reader          FileReader (read(char[] cbuf))                 BufferedReader (read(char[] cbuf) / readLine())
Writer          FileWriter (write(char[] cbuf,0,len)           BufferedWriter (write(char[] cbuf,0,len) / flush()

public class FileTest1 {
    @Test
    public void test1(){
        FileReader fr=null;
        try {
            //1.实例化file类的对象，指明要操作的文件
            File file = new File("hello.txt");
            //2.提供具体的流
            fr = new FileReader(file);
            //3.数据的读入
            //read():返回读入的一个字符，如果达到文件的末尾，则返回-1
            int data;
            while ((data=fr.read())!=-1){
                System.out.print((char)data);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fr!=null) {
                    fr.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

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@Test
    public void FileReaderTest(){
        FileReader fr = null;
        try {
            //1.实例化File类的对象
            File file = new File("hello.txt");
            //2.提供具体的流 FileRead流的具体实例化
            fr = new FileReader(file);
            //3.数据的读入
            int len;
            char[] cbuf = new char[5];
            //read(char cbuf[]):返回每次读入cbuf数组中的字符的个数，如果达到文件末尾，则返回-1
            while ((len=fr.read(cbuf))!=-1){
                for (int i = 0; i <len ; i++) {
                    System.out.print(cbuf[i]);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                //4.资源的关闭
                if (fr!=null) {
                    fr.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

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public class FileReader_ {
    /**
     * 单个字符读取文件
     */
    @Test
    public void fileReader01() {
        String filePath = "D:\\story.txt";
        FileReader fileReader = null;
        int data = 0;
        try {
            fileReader = new FileReader(filePath);
            //循环读取使用read,单个字符读取
            while ((data = fileReader.read()) != -1) {
                System.out.print((char) data);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fileReader != null) {
                    fileReader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
    /**
     * 使用字符数组读取文件
     */
    @Test
    public void fileReader02() {
        String filePath = "D:\\story.txt";
        FileReader fileReader = null;
        int readLen = 0;
        char[] buf = new char[8];
        try {
            fileReader = new FileReader(filePath);
            //循环读取使用read(buf),返回的是实际读取到的字符数
            //如果返回-1，说明文件结束
            while ((readLen = fileReader.read(buf)) != -1) {
                System.out.print(new String(buf, 0, readLen));
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (fileReader != null) {
                    fileReader.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}