java中的IO流

流分字节流与字符流

import org.omg.PortableInterceptor.SYSTEM_EXCEPTION;

import java.io.*;
import java.util.Properties;
import java.util.Set;

/**
 * @description:
 * @author: ljx
 * @time: 2020/7/13 16:35
 */
public class IoLearn {
    public static void main(String[] args) throws IOException {
//        test_io();
//        test_iobuf();
//        test_byte_io();
//        test_system_io();
//        test_system_io1()
        test_properties();

    }

    public static void test_io() throws IOException {
        //流分字节流和字符流，字节流InputStream，OutputStream,字符流抽象基类Reader,Writer
        //InputStream对应于Reader,OutputStream对应于Writer
        FileReader reader = new FileReader("C:\\Users\\hp\\IdeaProjects\\MyTests\\src\\main\\java\\demo.txt");
        FileWriter writer = new FileWriter("demo2.txt");
        char[] buf = new char[1024];
        int len = 0;
//        while((reader.read()!=-1)){
//            writer.write(reader.read());
//        }
        while ((len = reader.read(buf)) != -1) {
            writer.write(buf, 0, len);
        }
        reader.close();
        writer.close();
    }

    public static void test_iobuf() throws IOException {
        FileReader reader = new FileReader("C:\\Users\\hp\\IdeaProjects\\MyTests\\src\\main\\java\\demo.txt");
        BufferedReader bufferedReader = new BufferedReader(reader);
        FileWriter writer = new FileWriter("demo2.txt");
        BufferedWriter bufferedWriter = new BufferedWriter(writer);
        char[] buf = new char[1024];
        int len = 0;
//        while((reader.read()!=-1)){
//            writer.write(reader.read());
//        }
        String line = null;
        while ((line = bufferedReader.readLine()) != null) {
            bufferedWriter.write(line);
//            writer.write("\r\n");
            bufferedWriter.newLine();
            bufferedWriter.flush();
            bufferedWriter.flush();

        }
        reader.close();
        writer.close();
    }

    public static void test_byte_io() throws IOException {
        FileInputStream fileInputStream = new FileInputStream("1.png");
        BufferedInputStream bufferedInputStream = new BufferedInputStream(fileInputStream);
        FileOutputStream fileOutputStream = new FileOutputStream("2.png");
        BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(fileOutputStream);
        int len = 0;
        byte[] bytes = new byte[1024];
        while ((fileInputStream.read(bytes)) != -1) {
            fileOutputStream.write(bytes);
        }
        fileInputStream.close();
        fileOutputStream.close();

    }

    public static void test_system_io() throws IOException {
        //注意：单引号包裹的是char类型
        InputStream is = System.in;
        StringBuilder builder = new StringBuilder();
        int ch = 0;

        while ((ch = is.read()) != -1) {
            char c = (char) ch;
            if(ch=='\r'){
                continue;
            }
            if(ch=='\n') {

                String s = builder.toString();
                if(s.equals("over")){
                    break;
                }
                System.out.println(s.toUpperCase());
                builder.delete(0,builder.length());
            }else{
                builder.append(c);
            }
        }
    }
    public static void test_system_io1() throws IOException {
        //InputStreamReader,将字节流转换为字符流
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
        String line = null;
        while((line =reader.readLine())!=null){
            if(line.equals("over")){
                break;
            }
            writer.write(line.toUpperCase());
            writer.newLine();
            writer.flush();


        }
        reader.close();
        writer.close();

    }
    public static void  test_file() throws IOException {
        //File类用来将文件或者文件夹封装成对象，方便对文件与文件夹的属性信息进行操作
        File file = new File("demo3.txt");
        //文件分隔符，可根据操作系统进行更换
        System.out.println(File.separator);
        //文件名称
        System.out.println(file.getName());
        //绝对路径
        System.out.println(file.getAbsolutePath());
        //文件名
        System.out.println(file.getPath());
        //父级路径，如果此路径名没有指定父目录，则返回 null
        System.out.println(file.getParent());
        //文件大小
        System.out.println(file.length());
        //创建文件，不存在创建返回true
        System.out.println(file.createNewFile());
        //创建多级目录
        File dir = new File("aa\\bb");
        System.out.println(dir.mkdir());
        //判断文件是否存在，是否是文件，文件夹
        System.out.println(file.exists());
        System.out.println(file.isFile());
        System.out.println(file.isDirectory());
        File[] filse = File.listRoots();
        for(File file1 : filse){
            System.out.println(file1.getPath());
            System.out.println(file1.getTotalSpace());
            System.out.println(file1.getFreeSpace());
            System.out.println(file1.getUsableSpace());

        }
        //获取当前目录下的文件及文件夹名
        File file2= new File(".\\");
        String[] names = file2.list();
        for(String  file3 : names){
            System.out.println(file3);
        }


    }
    public static void test_properties() throws IOException {
        //键值对必须是字符串
        Properties p = new Properties();
        p.setProperty("zhangsan","20");
        p.setProperty("lisi","90");
        FileWriter writer = new FileWriter("a.properties");
        Set<String> names = p.stringPropertyNames();
        for(String name : names){
            System.out.println(p.getProperty(name));
            p.store(writer,name+p.getProperty(name));
        }
        

    }

}