getresult.java

编写一个简单的图书馆图书查询界面

package frank.simpleLibrary;

import java.io.*;
import java.awt.*;
import java.awt.event.*;
import java.text.DecimalFormat;

import javax.swing.*;

import frank.simpleLibrary.Book;

public class GetResult extends JFrame {
	private JTextArea display;
	private JButton exitButton;
	private JPanel buttonPanel;
	
	private ObjectInputStream input;
	private FileInputStream fileInput;
	private File fn;
	private String tit, auth;
	double prc_low, prc_high;
	
	//set up GUI and execute search
	public GetResult(String title, String author, double price_low, double price_high, File f) {
		super("查询结果");
		
		tit = title;
		auth = author;
		prc_low = price_low;
		prc_high = price_high;
		fn = f;
		
		
		Container c = getContentPane();
		
		//set up exit button
		buttonPanel = new JPanel();
		
		exitButton = new JButton("关闭");
		exitButton.addActionListener(
			new ActionListener() {
				public void actionPerformed(ActionEvent e) {
					if(input != null)
						closeFile();
					GetResult.this.dispose();
				}
			}
		);
		buttonPanel.add(exitButton);
		
		//set up display area
		display = new JTextArea();
		display.setEditable(false);
		JScrollPane scroller = new JScrollPane(display);
		
		//attach components to pane
		c.add(scroller, BorderLayout.CENTER);
		c.add(buttonPanel, BorderLayout.SOUTH);
		
		//register window listener
		addWindowListener(
			new WindowAdapter() {
				public void windowClosing(WindowEvent event) {
					if(input != null)
						closeFile();
					GetResult.this.dispose();
				}
			}
		);
		
		pack();
		setSize(600,250);
		setVisible(true);
		
		//show result;
		searchResult();
	}
	
	private void openFile() {
		try {
			//close file from previous operation
			if(input != null)
				input.close();
			fileInput = new FileInputStream(fn);
			input = new ObjectInputStream(fileInput);
		}
		
		//process exceptions
		catch(IOException ioE) {
			JOptionPane.showMessageDialog(this, "打开文件错误", "错误", JOptionPane.ERROR_MESSAGE);
		}
	}
	
	private void closeFile() {
		try {
			input.close();
		}
		//process exceptions
		catch(IOException ioE) {
			JOptionPane.showMessageDialog(this, "关闭文件错误", "错误", JOptionPane.ERROR_MESSAGE);
			System.exit(1);
		}
	}
	
	private void searchResult() {
		Book b;
		DecimalFormat twoDigits = new DecimalFormat("0.00");
		openFile();
		boolean found = false;
		
		//search books
		try {
			display.setText("查询条件：\n" +
					"书名包含：" + tit +
					"\t作者包含：" + auth +
					"\t价格范围：" + twoDigits.format(prc_low) +
					" 至 " + twoDigits.format(prc_high) + "\n\n");
			while(true) {
				//read a book record
				b = (Book)input.readObject();
				if(satisfied(b)){
					display.append(b.getTitle() + "\t\t\t"

							+ b.getAuthor() + "\t\t\t"
							+ twoDigits.format(b.getPrice()) + "\n");
					found = true;
				}
			}
		}
		//if end of file reached
		catch(EOFException eofE) {
			if(!found)
				display.append("没有满足条件的图书！");
			closeFile();
		}
		//process ClassNotFound exceptions
		catch(ClassNotFoundException cnfE) {
			JOptionPane.showMessageDialog(this, "读取文件时出错！", "错误", JOptionPane.ERROR_MESSAGE);
		}
		//process io exceptions
		catch(IOException ioE) {
			JOptionPane.showMessageDialog(this, "读取文件时出错！", "错误", JOptionPane.ERROR_MESSAGE);
		}
	} // end of searchResult
	
	//decide if a book record satisfy the inquiry conditions
	private boolean satisfied(Book b) {
		boolean title_yes = false, author_yes = false, price_yes = false;
		
		if(b.getTitle().indexOf(tit) >= 0 || tit.equals("")) title_yes = true;
		if(b.getAuthor().indexOf(auth) >= 0 || auth.equals("")) author_yes = true;
		if( (b.getPrice() >= prc_low && b.getPrice() <= prc_high)
				|| (prc_low == 0 && prc_high == 0)) price_yes = true;
		
		return title_yes && author_yes && price_yes;
	}
}