java生成字符串md5函数类（javaSE）

//实现生成MD5值
import java.io.BufferedInputStream;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
public class Digest {
	public Digest() {
		// TODO Auto-generated constructor stub
	}
	/**
	 * @param args
	 */
	public static StringBuilder check(String path) {
		// TODO Auto-generated method stub
		StringBuilder sb = new StringBuilder();
		byte[] size = null;
		StringBuilder noAlgorithm=new StringBuilder("无法使用MD5算法，这可能是你的JAVA虚拟机版本太低");
		StringBuilder fileNotFound=new StringBuilder("未能找到文件，请重新定位文件路径");
		StringBuilder IOerror=new StringBuilder("文件输入流错误");
		try {
			MessageDigest md5=MessageDigest.getInstance("MD5");//生成MD5类的实例
			File file = new File(path); //创建文件实例，设置路径为方法参数
			FileInputStream fs = new FileInputStream(file);
			BufferedInputStream bi = new BufferedInputStream(fs);
			ByteArrayOutputStream bo = new ByteArrayOutputStream();
			byte[] b = new byte[bi.available()]; //定义字节数组b大小为文件的不受阻塞的可访问字节数
			int i;
			//将文件以字节方式读到数组b中
			while ((i = bi.read(b, 0, b.length)) != -1)
			{
			}
			md5.update(b);//执行MD5算法
			for (byte by : md5.digest())
			{
			sb.append(String.format("%02X", by));//将生成的字节MD５值转换成字符串
			}
			bo.close();
			bi.close();
		} catch (NoSuchAlgorithmException e) {
			// TODO Auto-generated catch block
			return noAlgorithm;
		} catch (FileNotFoundException e) {
			// TODO Auto-generated catch block
			return fileNotFound;
		} catch (IOException e) {
			// TODO Auto-generated catch block
			return IOerror;
		}
        return sb;//返回MD５值
	}
}

//生成窗体类为主类
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.MouseEvent;
import java.awt.event.MouseListener;
import javax.swing.*;
import javax.swing.plaf.metal.MetalLookAndFeel;
public class MainFrame extends JFrame implements ActionListener,MouseListener{
 JTextField fileSource=new JTextField(36);
 JTextField produceMD5=new JTextField(36);
 JTextField showEqual=new JTextField("请在此处输入源MD5值",36);
 JButton choiceFile=new JButton("选择文件");
 JButton createMD5=new JButton("生成MD5");
 JButton judgement=new JButton("对比");
 JPanel panel;
 JFileChooser fileChooser=new JFileChooser();
	public MainFrame() {
		// TODO Auto-generated constructor stub
		super("MD5工具");
		//设置主窗体的观感为金属外观
			try {
				UIManager.setLookAndFeel(new MetalLookAndFeel());
			} catch (UnsupportedLookAndFeelException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		//窗体布局使用GridBagLayout
		GridBagLayout gbl=new GridBagLayout();
		GridBagConstraints gbc=new GridBagConstraints();
		panel=new JPanel(gbl);
		panel.setBorder(BorderFactory.createTitledBorder("xiaohb‘s MD5 check tool"));
		gbc.fill=GridBagConstraints.BOTH;
		gbc.weightx=1.0;
		gbc.weighty=1.0;
		gbl.setConstraints(fileSource, gbc);
		panel.add(fileSource);
		gbc.weightx=0.0;
		gbc.gridwidth=GridBagConstraints.REMAINDER;
		gbl.setConstraints(choiceFile, gbc);
		panel.add(choiceFile);
		gbc.gridwidth=1;
		gbl.setConstraints(produceMD5, gbc);
		panel.add(produceMD5);
		gbc.weightx=0.0;
		gbc.gridwidth=GridBagConstraints.REMAINDER;
		gbl.setConstraints(createMD5, gbc);
		panel.add(createMD5);
		gbc.gridwidth=1;
		gbl.setConstraints(showEqual, gbc);
		panel.add(showEqual);
		gbc.weightx=0.0;
		gbc.gridwidth=GridBagConstraints.REMAINDER;
		gbl.setConstraints(judgement, gbc);
		panel.add(judgement);
		add(panel);
		//给按钮添加注册器
		showEqual.addMouseListener(this);
		choiceFile.addActionListener(this);
		createMD5.addActionListener(this);
		judgement.addActionListener(this);
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
MainFrame frame=new MainFrame();
frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
frame.setSize(350, 200);
frame.setResizable(false);
frame.setVisible(true);
	}
	public void actionPerformed(ActionEvent e) {
		// TODO Auto-generated method stub
		Digest digest=new Digest();
		JOptionPane prompt=new JOptionPane();
		if(e.getSource()==choiceFile){
			fileChooser.showOpenDialog(this);
				fileSource.setText(fileChooser.getSelectedFile().toString());//显示选择的文件名
		}else if(e.getSource()==createMD5){
			produceMD5.setText((digest.check(fileSource.getText())).toString());//生成的MD5值显示在文本区域内
		}else if(e.getSource()==judgement){
			//判断MD5值是否相同
			if(produceMD5.getText().equalsIgnoreCase(showEqual.getText())){
				prompt.showMessageDialog(this, "两个MD5值相同，文件安全！");
			}else{
				prompt.showMessageDialog(this, "两个MD5值不同，文件可能被篡改，请检查！");
			}
		}
	}
	public void mouseClicked(MouseEvent e) {
		// TODO Auto-generated method stub
		if(e.getSource()==showEqual){
			showEqual.setText("");
		}
	}
	public void mouseEntered(MouseEvent arg0) {
		// TODO Auto-generated method stub

	}
	public void mouseExited(MouseEvent arg0) {
		// TODO Auto-generated method stub

	}
	public void mousePressed(MouseEvent arg0) {
		// TODO Auto-generated method stub

	}
	public void mouseReleased(MouseEvent arg0) {
		// TODO Auto-generated method stub

	}
}