IO知识点（五）—— Java的字符流 Reader，Writer

Reader字符输入流 

Writer字符输出流 

专门用于字符的形式读取和写入数据

1，使用字符流读取文件

FileReader 是Reader子类，以FileReader 为例进行文件读取 

// FileReader 继承 InputStreamReader
public class FileReader extends InputStreamReader{}

// InputStreamReader 继承 Reader
public class InputStreamReader extends Reader{}
           

public class AtWill {
 
	public static void main(String[] args) {
        // 准备文件lol.txt其中的内容是AB
        File f = new File("H:\\码云project\\gogo\\lala2.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) {
            e.printStackTrace();
        }
    }
}
           

2，使用字符流把字符串写入到文件

FileWriter 是Writer的子类，以FileWriter 为例把字符串写入到文件

// FileWriter 继承 OutputStreamWriter
public class FileWriter extends OutputStreamWriter{}

// OutputStreamWriter 继承 Writer
public class OutputStreamWriter extends Writer{}
           

public class AtWill {

	public static void main(String[] args) {
        // 准备文件lol2.txt
        File f = new File("H:\\码云project\\gogo\\lala2.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) {
            e.printStackTrace();
        }
    }
}
           

3，练习-文件加密，解密

public class AtWill {
	
	public static void encodeFile(File encodingFile, File encodedFile) throws IOException {
        FileReader fr = new FileReader(encodingFile);
        FileWriter fw = new FileWriter(encodedFile);
        try {
            char[] all = new char[(int) encodingFile.length()];
            char[] bll = new char[all.length];
            fr.read(all);
 
            for (int i = 0; i < all.length; i++) {
                bll[i] = all[i];
                if ((all[i] >= '0' && all[i]< '9') || (all[i] >= 'a' && all[i] < 'z') || (all[i] >= 'A' && all[i] < 'Z')) {
                    bll[i] = (char) (bll[i] + 1);
                } else if (all[i] == '9') {
                    bll[i] = '0';
                } else if (all[i] == 'Z') {
                    bll[i] = 'A';
                } else if (all[i] == 'z') {
                    bll[i] = 'a';
                }
            }
 
            fw.write(bll);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            fr.close();
            fw.close();
        }
    }
	
	public static void Decryption(File encodedFile,File encodingFile) {
        File f = new File(encodedFile.getAbsolutePath());
        if(!encodingFile.exists()) {
            encodingFile.canExecute();
        }
        char[] c = new char[(int)encodedFile.length()];
        try (FileReader fr = new FileReader(f)){
            fr.read(c);
            for (int i = 0; i < c.length; i++) {
                if(c[i]>'0'&c[i]<='9'|c[i]>'a'&c[i]<='z'|c[i]>'A'&c[i]<='Z') {
                    c[i]=(char)(c[i]-1);
                }
                else if(c[i]=='0') {
                    c[i]='9';
                }
                else if(c[i]=='A') {
                    c[i]='Z';
                }
                else if(c[i]=='a') {
                    c[i]='z';
                }
            }
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        File f1 =new File(encodingFile.getAbsolutePath());
        try(FileWriter fw = new FileWriter(f1)){
            fw.write(c);
        }catch(IOException e) {
            e.printStackTrace();
        }
    }

	public static void main(String[] args) {
      
        File f1 = new File("H:\\码云project\\gogo\\lala6.txt");
        File f2 = new File("H:\\码云project\\gogo\\lala8.txt");
//        try {
//			encodeFile(f1, f2);
//		} catch (IOException e) {
//			e.printStackTrace();
//		}
        Decryption(f1, f2);
  
    }
}
           

参考来源于：

http://how2j.cn/k/io/io-characterstream/341.html?p=48616