myactions.java

纯Java写的简易记事本,代码简单易懂,对初学JAVA者有很大帮助.两个.java同时编译运行就可以,无需修改

import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import java.io.File;
import java.util.Hashtable;
import java.util.Enumeration;
import javax.swing.filechooser.*;

public class MyActions {
	
//	static final long serialVersionUID = 3228193999994336070L;

	//	打开文件
	String fileOpen() {
		
		//	设置普通参数
		BufferedReader in = null;								//	设置读缓冲
		JFrame dialogFrame = new JFrame();				//	弹出窗口
		String filePath;												//	文件路径
		StringBuffer sbTemp = new StringBuffer(""); 	//	文件缓冲
		String sTemp = null;									//	行缓冲
		
		//	设置打开文件的扩展名 开始
		JFileChooser c = new JFileChooser();
		ExampleFileFilter filter = new ExampleFileFilter();
		filter.addExtension("txt");
		filter.setDescription("文本文件");
		c.setFileFilter(filter);
		//	设置打开文件的扩展名 结束

		int rVal = c.showOpenDialog(dialogFrame);
		if(rVal == JFileChooser.APPROVE_OPTION) {
			filePath = c.getSelectedFile().getPath();
			try{                                    //try ,catch 抛出，捕获 异常
				in = new BufferedReader(new FileReader(filePath));   //	文件路径
			} catch (FileNotFoundException e1) {
				e1.printStackTrace();             //抛出异常时执行的代码
			}
			
			try {
				while((sTemp = in.readLine()) != null ) {   //sTemp行缓冲
					sbTemp.append(sTemp + "\n");      //sbTemp文件缓冲
				}
			} catch (IOException e2) {
				e2.printStackTrace();
			}
			try {
				in.close();
			} catch (IOException e3) {
				e3.printStackTrace();
			}
		}
		return (sbTemp.toString());
	}

	//	保存文件
	void fileSave() {
		fileSaveAs();
	}
	
	String fileSaveAs() {
		//	设置普通参数
		JFrame dialogFrame = new JFrame();				//	弹出窗口
		StringBuffer filePath = new StringBuffer("");		//	文件路径
		
		//	设置保存文件的扩展名 开始
		JFileChooser c = new JFileChooser();
		ExampleFileFilter filter = new ExampleFileFilter();
		filter.addExtension("txt");
		filter.setDescription("文本文件");
		c.setFileFilter(filter);
		//	设置保存文件的扩展名 结束

		int rVal = c.showSaveDialog(dialogFrame);
		if(rVal == JFileChooser.APPROVE_OPTION) {
			filePath.append(c.getSelectedFile().getPath());
		}
		
		/*
		 * 	判断:
		 * 	如果保存文件的时候没有指示文件扩展名，则自动指示为.txt。
		 * 	如果保存文件的时候已经指示了文件扩展，则以指定方式保存。
		 */
		if ((filePath.lastIndexOf(".")) == -1) {
			filePath.append(".txt");
			return(filePath.toString());
		}
		else
			return (filePath.toString());
	}
	
	int fileNotSaveMessage(){
		int i;
		i = JOptionPane.showConfirmDialog(null, 
				"文件已经更改,想保存文件吗?", "记事本", JOptionPane.YES_NO_OPTION);
		return i;
	}
}

 class ExampleFileFilter extends FileFilter {

    private static String TYPE_UNKNOWN = "Type Unknown";
    private static String HIDDEN_FILE = "Hidden File";

    private Hashtable filters = null;
    private String description = null;
    private String fullDescription = null;
    private boolean useExtensionsInDescription = true;

 
    public ExampleFileFilter() {
	this.filters = new Hashtable();
    }

    public ExampleFileFilter(String extension) {
	this(extension,null);
    }

    public ExampleFileFilter(String extension, String description) {
	this();
	if(extension!=null) addExtension(extension);
 	if(description!=null) setDescription(description);
    }

    public ExampleFileFilter(String[] filters) {
	this(filters, null);
    }

    public ExampleFileFilter(String[] filters, String description) {
	this();
	for (int i = 0; i < filters.length; i++) {
	    // add filters one by one
	    addExtension(filters[i]);
	}
 	if(description!=null) setDescription(description);
    }

    public boolean accept(File f) {
	if(f != null) {
	    if(f.isDirectory()) {
		return true;
	    }
	    String extension = getExtension(f);
	    if(extension != null && filters.get(getExtension(f)) != null) {
		return true;
	    };
	}
	return false;
    }

     public String getExtension(File f) {
	if(f != null) {
	    String filename = f.getName();
	    int i = filename.lastIndexOf('.');
	    if(i>0 && i<filename.length()-1) {
		return filename.substring(i+1).toLowerCase();
	    };
	}
	return null;
    }

    
    public void addExtension(String extension) {
	if(filters == null) {
	    filters = new Hashtable(5);
	}
	filters.put(extension.toLowerCase(), this);
	fullDescription = null;
    }

    public String getDescription() {
	if(fullDescription == null) {
	    if(description == null || isExtensionListInDescription()) {
 		fullDescription = description==null ? "(" : description + " (";
		// build the description from the extension list
		Enumeration extensions = filters.keys();
		if(extensions != null) {
		    fullDescription += "." + (String) extensions.nextElement();
		    while (extensions.hasMoreElements()) {
			fullDescription += ", ." + (String) extensions.nextElement();
		    }
		}
		fullDescription += ")";
	    } else {
		fullDescription = description;
	    }
	}
	return fullDescription;
    }

    public void setDescription(String description) {
	this.description = description;
	fullDescription = null;
    }

    
    public void setExtensionListInDescription(boolean b) {
	useExtensionsInDescription = b;
	fullDescription = null;
    }

 
    public boolean isExtensionListInDescription() {
	return useExtensionsInDescription;
    }
}