• 文件与文件夹课后作业


    import java.util.ArrayList;
     
    public class Size {
       static long size=0;
     private static ArrayList<String> filelist=new ArrayList<String>();
     public static void main(String[] args) {
      Size s=new Size();
      String filePath="D:\软件";
      s.getFiles(filePath);
      
     }
     //通过递归得到某一路径下所有的目录及文件
     void getFiles(String filePath) {
      
      File root=new File(filePath);
      File[] files=root.listFiles();
      for(File file:files) {
       if(file.isDirectory()) {
        getFiles(file.getAbsolutePath());
        filelist.add(file.getAbsolutePath());
        
       }
       else {
        size+=file.getAbsolutePath().length();
       }
      }
      System.out.println("大小是"+size);
    
      
     }
       
    }

    这个程序的运行结果为:

    大小是431

    大小是868

    大小是964

    大小是1054

    大小是1254

    大小是1322

    大小是2013

    大小是2259

    大小是2338

    大小是2338

    大小是3655

    package shuruliu;
    import java.io.FileInputStream;  
    
    import java.io.FileOutputStream;  
    
    import java.io.InputStream;  
    
    import java.io.OutputStream;  
    
    import java.security.Key;  
    
    import java.security.SecureRandom;  
    
      
    
    import javax.crypto.Cipher;  
    
    import javax.crypto.CipherInputStream;  
    
    import javax.crypto.CipherOutputStream;  
    
    import javax.crypto.KeyGenerator;  
    public class JiaMi {
        Key key;   
    
          public void TestDES(String str) {   
    
            getKey(str);//生成密匙   
    
          }   
          public void getKey(String strKey) {   
    
                try {   
    
                    KeyGenerator _generator = KeyGenerator.getInstance("DES");   
    
                    _generator.init(new SecureRandom(strKey.getBytes()));   
    
                    this.key = _generator.generateKey();   
    
                    _generator = null;   
    
                } catch (Exception e) {   
    
                    throw new RuntimeException("Error initializing SqlMap class. Cause: " + e);   
    
                }   
    
              }   
          public void encrypt(String file, String destFile) throws Exception {   
    
                Cipher cipher = Cipher.getInstance("DES");   
    
                // cipher.init(Cipher.ENCRYPT_MODE, getKey());   
    
                cipher.init(Cipher.ENCRYPT_MODE, this.key);   
    
                InputStream is = new FileInputStream(file);   
    
                OutputStream out = new FileOutputStream(destFile);   
    
                CipherInputStream cis = new CipherInputStream(is, cipher);   
    
                byte[] buffer = new byte[1024];   
    
                int r;   
    
                while ((r = cis.read(buffer)) > 0) {   
    
                    out.write(buffer, 0, r);   
    
                }   
    
                cis.close();   
    
                is.close();   
    
                out.close();   
    
              }   
          public void decrypt(String file, String dest) throws Exception {   
    
                Cipher cipher = Cipher.getInstance("DES");   
    
                cipher.init(Cipher.DECRYPT_MODE, this.key);   
    
                InputStream is = new FileInputStream(file);   
    
                OutputStream out = new FileOutputStream(dest);   
    
                CipherOutputStream cos = new CipherOutputStream(out, cipher);   
    
                byte[] buffer = new byte[1024];   
    
                int r;   
    
                while ((r = is.read(buffer)) >= 0) {   
    
                    System.out.println();  
    
                    cos.write(buffer, 0, r);   
    
                }   
    
                cos.close();   
    
                out.close();   
    
                is.close();   
    
              }   
    
              public static void main(String[] args){   
    
                TestDES td = new TestDES();   
    
                try {
    
            td.encrypt("e:/r.txt", "e:/r加密后.txt");
    
            } catch (Exception e) {
    
            // TODO Auto-generated catch block
    
            e.printStackTrace();
    
            } //加密   
    
                try {
    
            td.encrypt("e:/r加密后.txt", "e:/r解密后.txt");
    
            } catch (Exception e) {
    
            // TODO Auto-generated catch block
    
            e.printStackTrace();
    
            } //解密   
    
                  
    
              }   
    
            }

    先建立一个文件,然后在文件里写入这个是要加密的文件,然后加密之后,形成一堆乱码,然后解密之后,文件里的内容又变为了,这个是要加密的文件。

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  • 原文地址:https://www.cnblogs.com/zhaoxinhui/p/9980146.html
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