JAVA GUI打开TXT文件使其内容显示在窗口的文本框内

JAVA初学者，想要实现如题目一样的需求，写一天了，网上能查到的方法都试了个遍，bufferedreader，filereader，fileinputstream都写了还是打不开文件，我在open那个地方的代码是有问题的，原本想着将字节数组转为string类型，后来发现编译不通过。代码不全，new和save都已实现就没有粘贴过来了，希望大家能给我改改，感谢!

package Txt;

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




public class TxtS {
    private File f1;
    private TextArea Tx;
    TxtS() {
        init();
    }

    public void init() {
        Frame f = new Frame("TXT tool");
        Tx = new TextArea();
        //Panel p1 = new Panel();
        
        FileDialog openDia = new FileDialog(f, "选择需要加载的文件", FileDialog.LOAD);
        FileDialog saveDia = new FileDialog(f, "选择你要保存的位置", FileDialog.SAVE);
        

        Button b3 = new Button("New");
        Button b4 = new Button("Open");
        Button b5 = new Button("Save");
        // Button b6 = new Button("A"); 暂缓处理改变字体

        //p1.setBounds(0, 0, 300, 800);
        f.setBounds(300, 100, 1200, 800);
        f.setLayout(new FlowLayout(FlowLayout.LEFT));
        Tx.setBounds(300, 0, 900, 800);
        f.setVisible(true);

        f.add(b3);
        f.add(b4);
        f.add(b5);
        f.add(Tx);
b4.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                openDia.setVisible(true);
                String dirPath = saveDia.getDirectory();
                String filename = saveDia.getFile();
                if (dirPath == null || filename == null)
                    return;
                Tx.setText(" "); // 清空文本
                //File f1 = new File(dirPath, filename);
                try {
                    // BufferedReader bufr = new BufferedReader(new FileReader(f1));
                    // String line;
                    // while ((line = bufr.readLine()) != null) {
                    //      Tx.append(line+ "\r\n");
                    //     Tx.setText(line);
                     //}
                    // bufr.close();
                    String path = dirPath+filename;
                    //FileReader reader = new FileReader(path) ;

                    FileInputStream fis = new FileInputStream(path);
                    byte[] bytes = new byte[fis.available()];
                    fis.read(bytes);
                    //StringBuffer result = new StringBuffer();
                    int len=0;
                    String[] s= new String(bytes);
                     while((len=fis.read(bytes))!=-1){
                        
                            Tx.setText(s);
                        }
                    //     Tx.append(bytes);
                    
                    // }
                    // fis.close();
                    //Tx.setText(result.toString());
                    System.out.println("读档成功！");
                } catch (IOException e1) {
                    throw new RuntimeException("打开失败！");
                }
                // catch(FileNotFoundException e1){
                //     e1.printStackTrace();
                // }
            }

        });

        // ----------------------------------------------------
        f.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                System.exit(0);
            }
        });
    }

    public static void main(String[] args) {
        new TxtS();    
    }

    
}

path输出看下是不是地址不对。