首先自定義一個OutputStream

import java.io.OutputStream;
import javax.swing.JTextArea;

/**
?*
?* @author?楊慶成?*/
public class GuiOutputStream extends OutputStream{
??? private JTextArea _text;
??? private byte _c;
??? private boolean _b=false;
???
??? /** Creates a new instance of GuiOutputStream */
??? public GuiOutputStream(JTextArea text) {
??????? _text=text;
??? }
???
??? public void write(int i){
??????? try{
??????????? byte c=(byte)i;
??????????? if(_b){
??????????????? _b=false;
??????????????? byte[] bs=new byte[2];
??????????????? bs[0]=_c;
??????????????? bs[1]=c;
??????????????? _text.append(new String(bs));
??????????? }
??????????? else if(c>0){
??????????????? _b=false;
??????????????? _text.append(String.valueOf((char)c));
??????????? }
??????????? else{
??????????????? _b=true;
??????????????? _c=c;
??????????? }
??????? }
??????? catch(Exception ex){
??????????? ex.printStackTrace();
??????? }
??? }
???
}

使用方式

重新定向OutputStream
??????? JTextArea jTextArea1 = new javax.swing.JTextArea();

??????? PrintStream out=new PrintStream(new GuiOutputStream(jTextArea1));
??????? System.setOut(out);

Log4j配置文件中Appender設置成org.apache.log4j.ConsoleAppender