Day22（File，DiGui，FileOutputStream）

One 、FileDemo1

package com.shujia.lhw.day22;

import java.io.File;

/*
     We want to achieve IO operation , You must know the form of files on the hard disk 
    java Provides a class that allows us to manipulate files on the hard disk ：File
    File That is, the form of document expression 

    File： Files and directories （ Folder ） Abstract representation of pathname 

     Construction method ：
      public File(String pathname)
         Create a new... By converting the given pathname string to an abstract pathname File example , If the given string is an empty string , The result is an empty abstract pathname 
      public File(String parent,String child)
         Create a new... From the parent pathname string and the child pathname string File example 
      public File(File parent,String child)
         Create a new... From the parent abstract pathname and child pathname strings File example 
 */
public class FileDemo1 {
    public static void main(String[] args) {
        //public File(String pathname) Get a from a path File object 
        //D:\a.txt Encapsulate into a File object 
        File file = new File("D:\\a.txt");
        System.out.println(file);

        //public File(String parent,String child)
        // The path of the parent ：D:\demo
        // The path of the child ：b.txt
        File file1 = new File("D:\\demo","b.txt");
        System.out.println(file1);

        //public File(File parent,String child)
        // The path of the parent ：D:\demo
        // The path of the word ：b.txt
        File file2 = new File("D:\\demo");
        File file3 = new File(file2,"b.txt");
        System.out.println(file3);
    }
}

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Two 、FileDemo2

package com.shujia.lhw.day22;

import java.io.File;
import java.io.IOException;

/*
     Create features ：
      public boolean createNewFile()
      public boolean mkdir()
      public boolean mkdirs()
 */
public class FileDemo2 {
    public static void main(String[] args) {
        // demand ： I want to D Create a folder under the disk demo2
        // Encapsulated into File object , Whether the file or directory already exists is not required , He just uses a path abstractly File Express 
        // In the future, you can use File Some methods in class , To create or delete 
        File file = new File("D:\\demo2");
        //public boolean mkdir() Create a directory named after this abstract path , If the destination folder already exists , We won't create , return false
        System.out.println(file.mkdir());

        //public boolean createNewFile() If and only if a file with that name does not already exist , Atomically create a new empty file named after the abstract pathname 
        try {
            System.out.println(file.createNewFile());
        } catch (IOException e) {
            e.printStackTrace();
        }

        // demand 2： I want to D Under the plate demo2 Create a file in the folder b.txt
        // Encapsulate the target file into File object 
        File file1 = new File("D:\\demo2\\b.txt");
//        try {
//            System.out.println(file1.createNewFile());
//        } catch (IOException e) {
//            e.printStackTrace();
//        }
//        System.out.println(file1.mkdir());

        //public boolean mkdirs() Create multi-level folders 
        File file2 = new File("D:\\demo2\\demo3\\demo4\\demo5");
        System.out.println(file2.mkdirs());

        // Be careful 1： Want to create a file in a directory , The premise is that the directory must exist ！！！
        File file3 = new File("D:\\demo3\\b.txt");
        try {
            System.out.println(file3.createNewFile());// The system could not find the specified path 
        } catch (IOException e) {
            e.printStackTrace();
        }
        // Be careful 2： In the future, you should find out whether you want to create files or folders , It's not necessarily the prince who rides the White Horse , There may also be Tang Monk 
    }
}

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3、 ... and 、FileDemo3

package com.shujia.lhw.day22;

import java.io.File;
import java.io.IOException;

/*
     Delete function ：
      public boolean delete()
 */
public class FileDemo3 {
    public static void main(String[] args) throws IOException {
        File file = new File("D:\\a.txt");
        System.out.println(file.delete());

        File file1 = new File("a.txt");
        System.out.println(file1.createNewFile());

        File file2 = new File("aaa\\bbb\\ccc");
        System.out.println(file2.mkdirs());
        System.out.println(file2.delete());

        File file4 = new File("aaa\\bbb");
        System.out.println(file4.delete());

        // demand ： I want to delete aaa This folder 
        // Be careful ： The directory to be deleted must be empty 
        File file3 = new File("aaa");
        System.out.println(file3.delete());
    }
}

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Four 、FileDemo4

package com.shujia.lhw.day22;

import java.io.File;

/*
     Rename function ：
      public boolean renameTo(File dest)
 */
public class FileDemo4 {
    public static void main(String[] args) {
        File file = new File("D:\\ftm.jpg");
        // Now I want to rename it von Timo .jpg
        File file1 = new File("D:\\ Feng Timo .jpg");
        System.out.println(file.renameTo(file1));
    }
}

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5、 ... and 、FileDemo5

package com.shujia.lhw.day22;

import java.io.File;
import java.sql.SQLOutput;

/*
     Judgment function ：
      public boolean isDirectory()
      public boolean isFile()
      public boolean exists()
      public boolean canRead()
      public boolean canWrite()
      public boolean isHidden()
 */
public class FileDemo5 {
    public static void main(String[] args) {
        File file = new File("a.txt");
//        File file = new File("b.txt");

        //public boolean isDirectory() Determine whether it is a folder 
        System.out.println(file.isDirectory());

        //public boolean isFile() Determine if it's a document 
        System.out.println(file.isFile());

        //public boolean exits() Determine whether the target file or folder exists 
        System.out.println(file.exists());

        //public boolean canRead() Judge whether it is readable 
        System.out.println(file.canRead());

        //public boolean canWrite() Judge whether it is writable 
        System.out.println(file.canWrite());

        //public boolean isHidden() Determine whether to hide 
        System.out.println(file.isHidden());
    }
}

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6、 ... and 、FileDemo6

package com.shujia.lhw.day22;

import java.io.File;
import java.text.SimpleDateFormat;
import java.util.Date;

/*
     Basic acquisition function ：
      public String getAbsolutePath()
      public String getPath()
      public String getName()
      public long length()
      public long lastModified()
 */
public class FileDemo6 {
    public static void main(String[] args) {
        File file = new File("a.txt");

        //public String getAbsolutePath() Get absolute path , Or full path 
        System.out.println(file.getAbsolutePath());

        //public String getName() Get the name 
        System.out.println(file.getName());

        //public long length() The length obtained is the number of bytes 
        System.out.println(file.length());

        //public long lastModified() What is returned is a timestamp , Accurate to milliseconds 
        System.out.println(file.lastModified());

        //java Convert timestamp to date 
        //Date(long date)
        // Allocate one Date object , And initialize it to indicate that it calls itself " Time " The specified number of milliseconds after the standard base time of , namely 1970 year 1 month 1 Japan 00:00:00 GMT
        Date date = new Date(file.lastModified());
        System.out.println(date);
        SimpleDateFormat sdf = new SimpleDateFormat("yyy-MM-ddHH:mm:ss");
        String format = sdf.format(date);
        System.out.println(format);
    }
}

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7、 ... and 、FileDemo7

package com.shujia.lhw.day22;

import java.io.File;

/*
     Advanced access 
      public String[] list()
      public File[] listFiles()
 */
public class FileDemo7 {
    public static void main(String[] args) {
        File file = new File("D:\\ Digital plus Technology \\ 15th issue ");

        //public String[] list() Gets an array of names of all files and folders in the specified directory 
        String[] list = file.list();
        for(String s : list){
            System.out.println(s);
        }
        System.out.println("=======================================");
        //public File[] listFile() Get all the files and folders in the specified directory File An array of objects 
        File[] files = file.listFiles();
        for(File f : files){
            System.out.println(f);
        }
    }
}

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8、 ... and 、FileDemo8

package com.shujia.lhw.day22;

import java.io.File;

/*
     Demand analysis ： Judge D Is there... Under the plate .jpg Later documents , If there is , Just output the file name 
      1、 take D The root directory is encapsulated into a File object 
      2、 Get all the files or folders in the directory File An array of objects 
      3、 Traverse File Array , Get every one File object , And then determine if it's a file 
         yes ： Continue to judge whether to use .jpg suffix 
           yes ： Output name 
             No ： Regardless of him 
         No ： Regardless of him 
 */
public class FileDemo8 {
    public static void main(String[] args) {
        File file = new File("D:\\");
        File[] files = file.listFiles();
        for(File f : files){
            if(f.isFile()){
                if (f.getName().endsWith(".jpg")){
                    System.out.println(f.getName());
                }
            }
        }
    }
}

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Nine 、FileDemo9

package com.shujia.lhw.day22;

import java.io.File;
import java.io.FilenameFilter;

/*
     First judge D Is there... Under the plate .jpg Later documents , Output the file name if any 
    1、 Get all the files and folders first , Then when traversing , Then judge whether it is a file , Whether it is .jpg Suffix , Finally, filter out the files that meet the conditions to obtain the name ,
    2、 At the time of acquisition , The data obtained meets the conditions , We can output it directly 

     Implementation idea and code of file name filter 
    public String[] list(FilenameFilter filter)
    public File[] listFile(FilenameFilter filter)
 */
public class FileDemo9 {
    public static void main(String[] args) {
        // establish File object 
        File file = new File("D:\\");

        //public String[] list(FilenameFilter filter)
        String[] list = file.list(new FilenameFilter() {
            @Override
            public boolean accept(File dir, String name) {
//                return false;
//                return true;
                // Found by test , Should the files or folders in the directory be obtained , Depending on the return value here 
                //true, Get the array , If it is false, Don't get , Not added to the array 
//                System.out.println(dir);
//                System.out.println(name);
                File file1 = new File(dir,name);
                boolean b = file.isFile();
                boolean b1 = name.endsWith(".jpg");
                return b && b1;
            }
        });

        for (String s : list){
            System.out.println(s);
        }
    }
}

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Ten 、DiGuiDemo1

package com.shujia.lhw.day22;
/*
     recursive ： Method defines the phenomenon of calling method itself 
    Math.max(Math.max(a,b)c) This phenomenon is only the nesting of methods, not the recursive use of methods 

     give an example ：
      1、 Once upon a time there was a mountain , There is a temple in the mountain , There is an old monk in the temple , The old monk is telling a story to the little monk , The content of the story is ：
          Once upon a time there was a mountain , There is a temple in the mountain , There is an old monk in the temple , The old monk is telling a story to the little monk , The content of the story is ：
          Once upon a time there was a mountain , There is a temple in the mountain , There is an old monk in the temple , The old monk is telling a story to the little monk , The content of the story is ：
         ...
          The temple fell down , The old monk passed away 

      2、 Learn big data -- High paid employment -- To earn money -- Marry a daughter-in-law -- Born baby -- Earn tuition ：
          Learn big data -- High paid employment -- To earn money -- Marry a daughter-in-law -- Born baby -- Earn tuition ：
          Learn big data -- High paid employment -- To earn money -- Marry a daughter-in-law -- Born baby -- Earn tuition ：
         ...
          Can't get a daughter-in-law , Can't have a baby 

     Recursion considerations ：
      1、 Recursion must have an exit （ The end condition ）, Otherwise it will be dead 
      2、 You can't recurse too many times , Otherwise, it will cause , Stack memory overflow 
      3、 Constructors cannot be recursive 

 */
public class DiGuiDemo1 {
//    public DiGuiDemo1(){
//        new DiGuiDemo1();
//    }

    // Dead recursion 
    public void show(){
        show();
    }
}

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11、 ... and 、DiGuiDemo2

package com.shujia.lhw.day22;
/*
     demand ： Find out the implementation with code 5 The factorial 
    5!=5*4*3*2*1
      =5*4!
      =5*4*3!
      =5*4*3*2!
      =5*4*3*2*1!

    1、 Solve with circulation 
    2、 Solve with recursion 
 */
public class DiGuiDemo2 {
    public static void main(String[] args) {
        int i = 1;
        for (int x = 2;x <= 5;x++){
            i = i*x;
        }
        System.out.println("5 The factorial is ："+i);

        // Use recursive method to realize 
        System.out.println("5 The factorial is ："+diGui(5));
    }

    /*
         The premise of recursive method ：
           return type ：int
           parameter list ：int i
           Export conditions ：if(i==1){return 1}
           Recursive topic logic ：
            if(i!=1){
              return i*deGui(i-1);
            }

     */
    public static int diGui(int i){
        if(i==1){
            return 1;
        }else {
            return i*diGui(i-1);
        }
    }
}

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Twelve 、DiGuiDemo3

package com.shujia.lhw.day22;
/*
     Undead rabbit case ：
       Suppose there are a pair of Rabbits , From the third month of life , A couple of rabbits are born every month , After the third month, the rabbit grows up , Another pair of rabbits are born every month 
       Suppose all rabbits don't die 
       problem ： Twenty months later , What are the logarithm of the rabbit ？

     Looking for a regular ：
       month       The number of Rabbits 
       First month     1
       The second month     1
       The third month     2
       The fourth month     3
       The fifth month     5
       The sixth month     8
      ...

       thus it can be seen , The logarithm of the rabbit is ：
        1,1,2,3,5,8,13,21,34...

       law ：
        1、 Start with the third item , Each is the sum of the first two 
        2、 Explain that the data of the first two items are known 

       How to achieve it ？
        1、 Array implementation 
        2、 Basic variable implementation 
        3、 Recursive implementation 

       Define two variables as adjacent data 
         The first 1 Adjacent data ：a=1,b=1
         The first 2 Adjacent data ：a=1,b=2
         The first 3 Adjacent data ：a=2,b=3
         The first 4 Adjacent data ：a=3,b=5

       law ： Next adjacent data ,a The value of is the last time b Value ,b The value of is the sum of the last adjacent data a+b

 */
public class DiGuiDemo3 {
    public static void main(String[] args) {
        // Implementation with array 
        int[] arr = new int[20];
        arr[0] = 1;
        arr[1] = 1;
//        arr[2] = arr[0] + arr[1];
//        arr[3] = arr[1] + arr[2];
//        //...
//        arr[19] = arr[17] + arr[18];
        for(int i = 2;i<arr.length;i++){
            arr[i] = arr[i-2] + arr[i-1];
        }
        System.out.println(" The first 20 The number of rabbits after months is ："+arr[19]);
        System.out.println("=============================================");

        // Basic variable implementation 
        // Next adjacent data ,a The value of is the last time b Value ,b The value of is the sum of the last adjacent data a+b
        int a = 1;
        int b = 1;
        for(int i = 1;i <= 18;i++){
            // Define a temporary variable , Store the last time a Value 
            int tmp = a;
            a = b;
            b = tmp + b;
        }
        System.out.println(" The number of rabbits after the 20th month is ："+b);
        System.out.println("=============================================");
        // Recursive form 
        System.out.println(" The number of rabbits after the twentieth month is ："+Fibonacci(20));
    }

    /*
         return type ：int
         parameter list ：int i 20
        <p>
         Export conditions ： The first month was 1, The second month is also 1
         The condition of recursion ： From the third month on , The value of each month is the sum of the first two months 
     */
    public static int Fibonacci(int i){//4
        // The first month was 1, The second month is also 1
        if(i ==1 | i == 2){
            return 1;
        }else {
            // From the third month on , The value of each month is the sum of the previous two months 
            return Fibonacci(i-1) + Fibonacci(i-2);
            //Fibonacci(3) + Fibonacci(2)
            //Fibonacci(2) + Fibonacci(1) + 1
            //1 + 1 + 1
            //3
        }
    }
}

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13、 ... and 、DiGuiDemo4

package com.shujia.lhw.day22;

import java.io.File;

/*
     Traverse all the file names with the specified suffix in the specified directory D：\ Digital plus Technology \ 15th issue 

     analysis ：
      1、 Encapsulate the directory into File object 
      2、 Get all under this directory File An array of objects 
      3、 Traverse the array to get each File object 
      4、 The result of judgment File Is the object a file or a folder 
        1） If it's a folder , Go back to step two 
        2） If he is a file , Judge whether the file name is marked with .java suffix 
           If it is , Output 
           If not , skip 
 */
public class DiGuiDemo4 {
    public static void main(String[] args) {
        // Encapsulate the directory into File object 
        File file = new File("D:\\ Shujia College \\ 15th issue ");

        // Recursive implementation 
        getJavaFile(file);
    }

    public static void getJavaFile(File file){
        // Get all under this directory File An array of objects 
        File[] files = file.listFiles();

        // Traverse the array to get each File object 
        for (File f : files){
            // Decide if it's a folder 
            if (f.isDirectory()){
                getJavaFile(f);
            }else{
                // Judge whether the file name is marked with .java suffix 
                if (f.getName().endsWith(".java")){
                    // If it is , Output 
                    System.out.println(f.getName());
                }
            }
        }
    }
}

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fourteen 、DiGuiDemo5

package com.shujia.lhw.day22;

import java.io.File;

/*
     Recursively delete directory with content ：

     analysis ：
      1、 obtain File object 
      2、 Get all the files and folders in the directory File An array of objects 
      3、 Traverse the array to get each File object 
      4、 Judge this File Whether the object is a folder 
         yes ： Go back to step two 
         No ： Delete directly 
 */
public class DiGuiDemo5 {
    public static void main(String[] args) {
        File file = new File("D:\\IdeaProjects\\bigdata15\\aaa");

        deleteFile(file);
    }
    public static void deleteFile(File file){
        // Get all the files and folders in the directory File An array of objects 
        File[] files = file.listFiles();

        if(files!=null){
            // Traverse the array to get each File object 
            for (File f : files){
                // Judge this File Whether the object is a folder 
                if(f.isDirectory()){
                    deleteFile(f);
                }else{
                    System.out.println(f.getName()+"---"+f.delete());
                }
            }
            System.out.println(file.getName()+"---"+file.delete());
        }
    }
}

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15、 ... and 、FileOutputStreamDemo1

package com.shujia.lhw.day22;

import java.io.File;
import java.io.FileOutputStream;

/*
    IO Classification of flows ：
       flow ：
         Input stream   Reading data 
         Output stream   Writing data 
       data type ：
         Byte stream 
           Byte input stream   Reading data  InputStream
           Byte output stream   Writing data  OutputStream
         Character stream 
           Character input stream   Reading data  Reader
           Character output stream   Writing data  Writer

     demand ： Go to a.txt Write a sentence in the file ：" big data ,yyds"

     analysis ：
      1、 Because it operates on text files , It's best to use character stream to do , But today we will focus on byte stream , Character stream is based on byte stream , Now it is realized by throttling 
      2、 We're going to write a sentence to the file , You need to use the output stream , Here is the byte output stream 

     Through the above analysis , Final lock OutputStream
     Observe API After the discovery ,OutputStream Is an abstract class , Can't be instantiated directly 
    FileOutputStream:
       Construction method ：
        FileOutputStream(File file) Create a file output stream to write to the specified File File represented by object 
        FileOutputStream(String name) Create a file output stream to write to the file with the specified name 

       Steps of byte output stream ：
        1、 Create byte output stream object 
        2、 Calling method , Writing data 
        3、 Release resources 
 */
public class FileOutputStreamDemo1 {
    public static void main(String[] args) throws Exception{
        // Create a byte stream output object 
        //FileOutputStream(File file) Creates a file output stream to write to the File File represented by object 
        File file = new File("b.txt");
        // If the target file does not exist , Automatically create 
//        FileOutputStream fos = new FileOutputStream(file);
        //FileOutputStream(String name) Create a file output stream to write to the file with the specified name 

        // If the target file does not exist , Automatically create 
        FileOutputStream fos = new FileOutputStream("c.txt");
//        System.out.println(fos);

        // Calling method , Writing data 
        fos.write(" big data ,yyds".getBytes());

        // Release resources 
        //close() Close this file output stream and free any system resources associated with this stream 
        fos.close();

        fos.write(" Continue writing ".getBytes());
    }
}

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sixteen 、FileOutputStreamDemo2

package com.shujia.lhw.day22;

import java.io.FileOutputStream;

/*
     Several methods of writing data in byte output stream ：
      public void write(int b)
      public void write(byte[] b)
      public void write(byte[] b,int off,int len)
 */
public class FileOutputStreamDemo2 {
    public static void main(String[] args) throws Exception{
        // Create byte output stream object 
        FileOutputStream fos = new FileOutputStream("d.txt");

        //public void write(int b)
        //97, The binary stored at the bottom ,97 Corresponding ASCII The character of the code is a
        fos.write(97);
        fos.write(48);
        fos.write(65);

        //public void write(byte[] b)
        byte[] bytes = {97,98,99,100,101};
        fos.write(bytes);

        //public void write(byte[] b,int off,int len)
        // From at offset off Writes the specified byte array of len Bytes to the file output stream 
        fos.write(bytes,1,3);

        // Release resources 
        fos.close();
    }
}

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seventeen 、FileOutputStreamDemo3

package com.shujia.lhw.day22;

import java.io.FileOutputStream;

/*
    1、 How to realize line feed ？
       Want to know why there is no line feed ？ Because we only write bytes of data , No newline is written 
       How to achieve it ？ At the writing Festival , Add a line break , Be careful ： Different systems , Line breaks are not necessarily the same 
      Mac:\r
      Windows:\r\n
      Linux:\n

    2、 How to implement addition ？

 */
public class FileOutputStreamDemo3 {
    public static void main(String[] args) throws Exception {
        // Create byte output stream object 
//        FileOutputStream fos = new FileOutputStream("e.txt");
//        fos.write(" big data 1,yyds".getBytes());
//        fos.write("\r\n".getBytes());
//        fos.write(" big data 2,yyds".getBytes());

        //FileOutputStream(String name,boolean append)
        // Create a file output stream to write to the file with the specified name 
        //true It means that data can be added and written 
        FileOutputStream fos = new FileOutputStream("e.txt", true);
        fos.write("\r\n it's snowing today \r\n".getBytes());
//        fos.write("\r\n".getBytes());
        fos.write(" But I didn't see the snow ".getBytes());

        // Release resources 
        fos.close();
        //...
    }
}