Java self -I / O stream of characters

Java character stream Reader Writer

Reader character input stream
Writer character output stream
dedicated to the character in the form of read and write data

Step 1: Use character stream to read the file

FileReader is a subclass of Reader to read the file FileReader example.

package stream;
 
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
 
public class TestStream {
 
    public static void main(String[] args) {
        // 准备文件lol.txt其中的内容是AB
        File f = new File("d:/lol.txt");
        // 创建基于文件的Reader
        try (FileReader fr = new FileReader(f)) {
            // 创建字符数组，其长度就是文件的长度
            char[] all = new char[(int) f.length()];
            // 以字符流的形式读取文件所有内容
            fr.read(all);
            for (char b : all) {
                // 打印出来是A B
                System.out.println(b);
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
 
    }
}

Step 2: Use a character string is written to the stream file

Writer FileWriter is a subclass to Example FileWriter writes a string to a file

package stream;
  
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
  
public class TestStream {
  
    public static void main(String[] args) {
        // 准备文件lol2.txt
        File f = new File("d:/lol2.txt");
        // 创建基于文件的Writer
        try (FileWriter fr = new FileWriter(f)) {
            // 以字符流的形式把数据写入到文件中
            String data="abcdefg1234567890";
            char[] cs = data.toCharArray();
            fr.write(cs);
  
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
  
    }
}

Exercise : File Encryption

Prepare a text file (non-binary), which contains the ASCII characters and Chinese characters.
A design method

public static void encodeFile(File encodingFile, File encodedFile);

In this method the encodingFile encrypt the contents, and then save the file to encodedFile.
Encryption Algorithm:
Digital:
If the number is not 9, adding 1 to the original basis, such as into 6 5, 3 becomes 4
if numbers 9, becomes 0
alphabetic characters:
if the character is non-z, a rightward such as d into e, G to H
if z, z-> a, ZA.
Characters need to keep sensitive
non-alphanumeric characters:
for example, '& ^ remain unchanged, Chinese also remain unchanged

answer:

package stream;
 
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
 
public class TestStream {
    /**
     *
     * @param encodingFile
     *            被加密的文件
     * @param encodedFile
     *            加密后保存的位置
     */
    public static void encodeFile(File encodingFile, File encodedFile) {
 
        try (FileReader fr = new FileReader(encodingFile); FileWriter fw = new FileWriter(encodedFile)) {
            // 读取源文件
            char[] fileContent = new char[(int) encodingFile.length()];
            fr.read(fileContent);
            System.out.println("加密前的内容：");
            System.out.println(new String(fileContent));
 
            // 进行加密
            encode(fileContent);
            // 把加密后的内容保存到目标文件
            System.out.println("加密后的内容：");
            System.out.println(new String(fileContent));
 
            fw.write(fileContent);
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
 
    private static void encode(char[] fileContent) {
        for (int i = 0; i < fileContent.length; i++) {
            char c = fileContent[i];
            if (isLetterOrDigit(c)) {
                switch (c) {
                case '9':
                    c = '0';
                    break;
                case 'z':
                    c = 'a';
                    break;
                case 'Z':
                    c = 'A';
                    break;
                default:
                    c++;
                    break;
                }
            }
            fileContent[i] = c;
        }
    }
 
    public static boolean isLetterOrDigit(char c) {
        // 不使用Character类的isLetterOrDigit方法是因为，中文也会被判断为字母
        String letterOrDigital = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
        return -1 == letterOrDigital.indexOf(c) ? false : true;
    }
 
    public static void main(String[] args) {
        File encodingFile = new File("E:/project/j2se/src/Test1.txt");
        File encodedFile = new File("E:/project/j2se/src/Test2.txt");
        encodeFile(encodingFile, encodedFile);
    }
}