java截获控制台输出

[kared]

package org.com.consoleTextArea;

import java.awt.TextArea;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.PrintStream;

import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JScrollPane;
import javax.swing.text.Document;

public class ConsoleTextArea extends TextArea {
	public ConsoleTextArea(InputStream[] inStreams) {
		for (int i = 0; i < inStreams.length; ++i)
			startConsoleReaderThread(inStreams[i]);
	} // ConsoleTextArea()

	public ConsoleTextArea() throws IOException {
		final LoopedStreams ls = new LoopedStreams();
		// redirect System.out and System.err
		PrintStream ps = new PrintStream(ls.getOutputStream());
		System.setOut(ps);
		System.setErr(ps);
		startConsoleReaderThread(ls.getInputStream());
	} // ConsoleTextArea()

	private void startConsoleReaderThread(InputStream inStream) {
		final BufferedReader br = new BufferedReader(new InputStreamReader(
				inStream));
		new Thread(new Runnable() {
			public void run() {
				StringBuffer sb = new StringBuffer();
				try {
					String s;
					Document doc =getDocument();
					while ((s = br.readLine()) != null) {
						boolean caretAtEnd = false;
						caretAtEnd = getCaretPosition() == doc.getLength() ? true
								: false;
						sb.setLength(0);
						append(sb.append(s).append('\n').toString());
						if (caretAtEnd)
							setCaretPosition(doc.getLength());
					}
				} catch (IOException e) {
					JOptionPane.showMessageDialog(null,
							"read from BufferedReader err：" + e);
					System.exit(1);
				}
			}
		}).start();
	} // startConsoleReaderThread()
 // ConsoleTextArea
public static void main(String[] args) {
    JFrame f = new JFrame("ConsoleTextArea测试");
    ConsoleTextArea consoleTextArea = null;
    try {
        consoleTextArea = new ConsoleTextArea();
    }
    catch(IOException e) {
        System.err.println(
            "不能创建LoopedStreams：" + e);
        System.exit(1);
    }
    consoleTextArea.setFont(java.awt.Font.decode("monospaced"));
    f.getContentPane().add(new JScrollPane(consoleTextArea),
        java.awt.BorderLayout.CENTER);
    f.setBounds(50, 50, 300, 300);
    f.setVisible(true);
    f.addWindowListener(new java.awt.event.WindowAdapter() {
        public void windowClosing(
            java.awt.event.WindowEvent evt) {
            System.exit(0);
        }
    });
    // 启动几个写操作线程向
    // System.out和System.err输出
    startWriterTestThread(
        "写操作线程 #1", System.err, 920, 50);
    startWriterTestThread(
        "写操作线程 #2", System.out, 500, 50);
    startWriterTestThread(
        "写操作线程 #3", System.out, 200, 50);
    startWriterTestThread(
        "写操作线程 #4", System.out, 1000, 50);
    startWriterTestThread(
        "写操作线程 #5", System.err, 850,    50);
} // main()
private static void startWriterTestThread(
    final String name, final PrintStream ps, 
    final int delay, final int count) {
    new Thread(new Runnable() {
        public void run() {
            for(int i = 1; i <= count; ++i) {
                ps.println("***" + name + ", hello !, i=" + i);
                try {
                    Thread.sleep(delay);
                }
                catch(InterruptedException e) {}
            }
        }
    }).start();
} // startWriterTestThread()
} // ConsoleTextArea

package org.com.consoleTextArea;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;

public class LoopedStreams {
	private PipedOutputStream pipedOS =
			  new PipedOutputStream();
			 private boolean keepRunning = true;
			 private ByteArrayOutputStream byteArrayOS =
			  new ByteArrayOutputStream() {
			  public void close() {
			   keepRunning = false;
			   try {
			    super.close();
			    pipedOS.close();
			   }
			   catch(IOException e) {
			    
			    System.exit(1);
			   }
			  }
			 };

			 private PipedInputStream pipedIS = new PipedInputStream() {
			  public void close() {
			   keepRunning = false;
			   try {
			    super.close();
			   }
			   catch(IOException e) {
			    
			    System.exit(1);
			   }
			  }
			 };

			 public LoopedStreams() throws IOException {
			  pipedOS.connect(pipedIS);
			  startByteArrayReaderThread();
			 } // LoopedStreams()

			 public InputStream getInputStream() {
			  return pipedIS;
			 } // getInputStream()

			 public OutputStream getOutputStream() {
			  return byteArrayOS;
			 } // getOutputStream()

			 private void startByteArrayReaderThread() {
			  new Thread(new Runnable() {
			   public void run() {
			    while(keepRunning) {
			     // check the number of bytes in the stream
			     if(byteArrayOS.size() > 0) {
			      byte[] buffer = null;
			      synchronized(byteArrayOS) {
			       buffer = byteArrayOS.toByteArray();
			       byteArrayOS.reset(); // clear the buffer
			      }
			      try {
			       // send the data to PipedOutputStream
			       pipedOS.write(buffer, 0, buffer.length);
			      }
			      catch(IOException e) {
			       // record the err or other things
			       // for simple, we just exit here
			       System.exit(1);
			      }
			     }
			     else // no data to read, then the thread go to sleep
			      try {
			       // check the ByteArrayOutputStream for new data every one second
			       Thread.sleep(1000);
			      }
			      catch(InterruptedException e) {}
			     }
			    }
			  }).start();
			 } // startByteArrayReaderThread()
			} // LoopedStreams

这是我在网上找的关于java截获控制台输出的代码，关联了textarea，但是在代码中ConsoleTextArea类中Document doc =getDocument();这句话一直报错，小弟不知道是什么原因，希望解决下。

[霜之哀伤]

目测函数没有定义 话说这种错误，肯定有错误信息的，楼主看不懂？

[kared]

没人帮忙吗！！

[安特矮油]

看看异常是什么信息，然后再根据异常说的问题来解决