fileencrypt.java

java经典10例子

import javax.swing.JOptionPane;
import java.io.*;

public class FileEncrypt{
	public static void main(String[] args) {
		//通过用户输入获取加密码文件、被加密的文件、加密后的文件
		String fdCode = InputReader.inputText("保存加密码的文件:");
		String fdOrig = InputReader.inputText("被加密的文件:");
		String fdResult = InputReader.inputText("加密后的文件:");
		try {
			//根据加密码进行文件加密
			Text aText = new Text(fdCode,fdOrig,fdResult);
			aText.encrypt();
			String toBePrinted = "被加密的文本内容:\n";
			toBePrinted += aText.getOriginalText();
			toBePrinted += "\n\n加密后的文本内容:\n";
			toBePrinted += aText.getEncryptedText();
			
			JOptionPane.showMessageDialog(null, toBePrinted);
		}catch(IOException e) {
			System.out.println(e.toString());
		}
		System.exit(0);
	}
}

//文本类
class Text {
	final String alphabet = "abcdefghijklmnopqrstuvwxyz";
	String code;
	String resultFileName;
	String originalText = "";
	String encryptedText = "";
	
	public Text(String codeFile, String originalFileName,
		String startResultFileName) throws IOException{
		resultFileName = startResultFileName;
		originalText = readText(originalFileName);
		code = readText(codeFile);
		//加密码长度应等于26
		if(code.length() != alphabet.length()) throw new IOException("非法的加密码.");
	}
	
	//获取被加密文件的文本
	public String getOriginalText() {
		return originalText;
	}
	
	//获取加密后文件的文本
	public String getEncryptedText() {
		return encryptedText;
	}
	
	public String readText(String filename) throws IOException {
		FileReader readCon = new FileReader(filename);
		BufferedReader reader = new BufferedReader(readCon);
		String text = "";
		
		String line = reader.readLine();
		while(line != null) {
			text += line + "\n";
			line = reader.readLine();
		}
		
		//将文本的最后一个字符删除，即文本最后不能以CR结尾
		text = text.substring(0,text.length()-1);
		reader.close();
		return text;
	}
	
	//根据给定的加密码进行文件加密
	public void encrypt() throws IOException {
		StringBuffer result = new StringBuffer();
		for(int i = 0; i < originalText.length(); i++) {
			boolean big = Character.isUpperCase(
				originalText.charAt(i));

			int pos = alphabet.indexOf(
				Character.toLowerCase(originalText.charAt(i)));
			if(pos > -1) {
				if(big) 
					result.append(
						Character.toUpperCase(code.charAt(pos)));
				else 
					result.append(code.charAt(pos));
			}else 
				result.append(originalText.charAt(i));
		}
		encryptedText = result.toString();
		//将加密后的结果输出到文件
		FileWriter resultConnection = new FileWriter(resultFileName, false);
		PrintWriter resultWriter = new PrintWriter(
			new BufferedWriter(resultConnection));
		resultWriter.print(encryptedText);
		resultWriter.close();
	}
}

class InputReader {
	public static String inputText(String prompt) {
		String text = JOptionPane.showInputDialog(prompt);
		while (text == null || text.trim().equals("")) {
			JOptionPane.showMessageDialog(null, "你未输入了文件名!");
			text = JOptionPane.showInputDialog(prompt);
		}
		return text.trim();
	}
	
	public static int inputInteger(String prompt) {
		int number = 0;
		boolean ok = false;
		do {
			String theInputText = inputText(prompt);
			try {
				number = Integer.parseInt(theInputText);
				ok = true;
			} catch (NumberFormatException e) {
				JOptionPane.showMessageDialog(null, "无效的整数!\n");
			}
		} while (!ok);
		return number;
	}
	
	public static double inputDecimalNumeral(String prompt) {
		double number = 0;
		boolean ok = false;
		do {
			String theInputText = inputText(prompt);
			try {
				number = Double.parseDouble(theInputText);
				ok = true;
			} catch (NumberFormatException e) {
				JOptionPane.showMessageDialog(null, "无效的浮点数!\n");
			}
		} while (!ok);
		return number;
	}
}

/* Example run:
***Input: File containing the encryption code: code.txt
***Input: File containing the text: original.txt
***Input: File to contain the result:: result.txt

The code file:
abcdefghijklmnopqrUtuvwxyz  // simple to test, only one letter is substituted

Encrypt:
Simon Thoresen
Thomas Angells gate 12
7011 Trondheim

The encrypted version of the text:
Uimon ThoreUen
ThomaU AngellU gate 12
7011 Trondheim
*/