帮忙分析一下这段代码！！！！
运行下面的程序出现了以下的情况

Java code

Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1    at java.lang.String.substring(String.java:1958)    at java.lang.String.substring(String.java:1925)    at java.awt.TextArea.replaceText(TextArea.java:390)    at java.awt.TextArea.replaceRange(TextArea.java:377)    at TextAreaDemo.<init>(TextAreaDemo.java:13)    at TextAreaDemo.main(TextAreaDemo.java:29)

Java code

import java.awt.*;public class TextAreaDemo extends Frame{TextArea textarea1=new TextArea(3,20);TextArea textarea2=new TextArea("Second",3,15);TextArea textarea3=new TextArea("Trid",2,10);TextArea textarea4=new TextArea("Fourth",2,10,TextArea.SCROLLBARS_BOTH);TextArea textarea5=new TextArea(2,10);TextAreaDemo(){    setLayout(new FlowLayout());    textarea3.replaceRange("HelloWorld",0 ,5);    textarea4.insert(" ", 3);    textarea5.append("Fifth");        add(textarea1);    add(textarea2);    add(textarea3);    add(textarea4);    add(textarea5);    setSize(400,200);    this.setVisible(true);    }         public static void main(String[] args) {        // TODO Auto-generated method stub        new TextAreaDemo();    }}

[解决办法]
TextArea textarea3=new TextArea("Trid",2,10);
初始值是Trid
textarea3.replaceRange("HelloWorld",0 ,5);
从第0个到第5个之间的内容，替换成HelloWorld，问题是Trid不够长啊！怎么截取？