文章目录

• 字符字节流，前升后降
• 一、pandas是什么？

字符字节流，前升后降

浏览器下载需要设置两个头 responese .setHeader() 一个设置返回的文件类型

		FileInputStream fis = new FileInputStream(path);
        
        //创建字节输出流
        ServletOutputStream sos = response.getOutputStream();
		
		
        //执行输出操作
        int len = 1;
        byte[] b = new byte[1024];
        while((len = fis.read(b)) != -1) {
            sos.write(b, 0, len);
        }
        
        /*方法内可以不关流*/
        sos.close();

		//告知客户端要下载的文件
		response.setHeader("content-disposition", "attachment;filename=" + filename);
		response.setHeader("content-type", "application/octet-stream");  

	

text/plain 表示文本文件的默认值。
application/octet-stream 表示所有其他情况的默认值

https://blog.csdn.net/qq_39007603/article/details/128566928

https://blog.csdn.net/woacptp/article/details/80199713

一、pandas是什么？

package Sort;

import com.sun.deploy.util.StringUtils;
import org.omg.IOP.Encoding;

import java.io.*;
import java.lang.reflect.Field;
import java.util.*;
import java.util.function.Consumer;

public class Sort {

    public static void main(String[] args) throws IOException {

        //test01();
        //test02();
        //test03();
       // test04();
        test06();
    }


    public static void test01(){

        Integer[] ints = new Integer[]{2,3,45,20,12321,1};
//        Arrays.sort(ints,Collections.reverseOrder());
//        Collections.sort(Arrays.asList(ints), new Comparator<int[]>() {
//            @Override
//            public int compare(int[] o1, int[] o2) {
//                return 0;
//            }
//        });
        //lambda
//        Arrays.stream(ints).forEach(value -> System.out.println(value));
        //o1-o2 是升序
        //o2-o1 是降序

        //lambda
        Arrays.stream(ints).sorted(new Comparator<Integer>() {
            @Override
            public int compare(Integer o1, Integer o2) {
                return o2-o1;   //是什么排序？？？？？？
            }
        }).forEach(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) {
                System.out.println(integer);
            }
        });
    }



    public static void test02(){
        List<Student> list = new ArrayList<>();
        list.add(new Student(1, "A", 20, 180));
        list.add(new Student(2, "B", 23, 175));
        list.add(new Student(3, "C", 22, 190));
        list.add(new Student(4, "D", 21, 175));
        list.add(new Student(5, "E", 20, 185));

        list.stream().sorted(new Comparator<Student>() {
            @Override
            public int compare(Student o1, Student o2) {
                //前升后降
                //身高升序，年龄升序
                if(o1.getHeight() == o2.getHeight()){
                    return o1.getAge()-o2.getAge();
                }else{
                    return o1.getHeight() - o2.getHeight();
                }

            }
        }).forEach(new Consumer<Student>() {
            @Override
            public void accept(Student student) {
                System.out.println(student);
            }
        });
    }


    public static void test03(){

        System.out.println("_wrhwiefwi".matches("^([A-Za-z0-9_]{1,})$"));
        

    }

    public static void test04() throws IOException {

        //降sql读取到该本地中去
        String sql = "select * from user limit 10";
        ByteArrayInputStream byteArrayInputStream = new ByteArrayInputStream(sql.getBytes());

        int length = 0 ;
        byte[] arr = new byte[1024];
        String fileName = "./"+ UUID.randomUUID()+".sql";

        FileOutputStream fileOutputStream = new FileOutputStream(fileName);

        while ( (length = byteArrayInputStream.read(arr)) != -1 ){
            fileOutputStream.write(arr,0,length);
        }
        //关闭流
        byteArrayInputStream.close();
        fileOutputStream.close();
    }


    public static void test05() throws IOException {

        //降sql读取到该本地中去
        String sql = "select * from user limit 10";
        StringReader stringReader = new StringReader(sql);
        FileWriter fileWriter = new FileWriter("./test05.sql");

        int length = 0;
        char[] chars = new char[1024];
        while( (length = stringReader.read(chars)) != -1 ){
            fileWriter.write(chars,0,length);
        }

        stringReader.close();
        fileWriter.close();

    }


    public static void test06() throws IOException {

        FileReader reader = new FileReader("./test05.sql");
        BufferedReader bufferedReader = new BufferedReader(reader);
        FileWriter writer = new FileWriter("./test06.sql",true);
        BufferedWriter bufferedWriter = new BufferedWriter(writer);


        String name = "";
         while ( (name = bufferedReader.readLine()) != null ){
             bufferedWriter.write(name);
             bufferedWriter.newLine();  //添加
             System.out.println(name);
         }

         bufferedWriter.flush();
            bufferedReader.close();
            bufferedWriter.close();

    }






}