properties

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.Properties;

public class MyProperties extends ArrayList {
    private String fileName;
    private String code = "GBK";
 public static void main(String[] args) throws IOException{
     String pathString="D:/proper.properties";
     MyProperties proper=new MyProperties(pathString,"GBK");
     proper.setTitle("测试用Properties设置键值对的值");
     proper.setProperties("studentName", "珍妮");
     proper.setNotes("studentName","学生姓名");
     proper.setProperties("room", "三年级一班");
     proper.setNotes("room", "所在年级");
     proper.setProperties("score", "98.5");
     proper.setNotes("score", "数学分数");
     proper.saveFile();
     System.out.println(readFile(pathString,"GBK"));
     proper.getValue();
     
     
 }
    public MyProperties(String fileName, String Code)
            throws UnsupportedEncodingException {
        this.setFileName(fileName);
        this.setCharacterEncoding(Code);

    }

    private void setFileName(String fileName) {
        this.fileName = fileName;
    }

    private void setCharacterEncoding(String code)
            throws UnsupportedEncodingException {
        new String("".getBytes("iso8859_1"), code);
        this.code = code;
    }

    public static boolean isExist(String fileName) {
        return new File(fileName).isFile();
    }

    public static String readFile(String fileName, String code)
            throws IOException {
        StringBuffer sb = new StringBuffer();// 创建字符缓冲流
        BufferedReader in = new BufferedReader(new FileReader(fileName));// 创建缓冲读对象
        String s;
        while ((s = in.readLine()) != null) {// 循环读取文件信息
            sb.append(s);// 拼接字符串
            sb.append("\n");
        }
        in.close();
        return sb.toString();
    }

    public void writeFile(String proper) throws IOException {// 字符串写入文件
        PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(
                fileName)));// 创建文本输入流打印对象
        out.print(proper);// 将字符串写入文件
        out.close();// 释放资源
    }

    public void saveFile() throws IOException {
        PrintWriter out = new PrintWriter(new BufferedWriter(new FileWriter(
                fileName)));
        String tmpString;
        for (int i = 0; i < size(); i++) {
            tmpString = get(i) + "";
            out.println(tmpString);
        }
        out.close();
    }

    public void setProperties(String key, String val)
            throws UnsupportedEncodingException {// 设置Properties键值
        int pro = LookForKey(key);
        if (pro >= 0) {
            this.set(pro, key + "=" + val);
        } else {
            this.add(key + "=" + val);
        }

    }

    public int LookForKey(String key) throws UnsupportedEncodingException {// 查找键的序号
        String tempString;
        for (int i = 0; i < size(); i++) {// 循环显示集合的信息
            tempString = get(i) + "";
            tempString = new String(tempString.getBytes("iso8859_1"), code);// 编码转换
            if (tempString.indexOf(key) == 0) {// 没有找到键值对
                return i;
            }

        }
        return -1;
    }

    public void setNotes(String key, String memo)
            throws UnsupportedEncodingException {// 设置备注
        if ("".equals(key)) {
            this.add("#" + memo);
            return;
        }
        String tempString;
        int result = LookForKey(key);
        if (result == -1) {
            this.add("#" + memo);
            this.add(key + "=");
        } else {
            int postion = result - 1;
            if (postion < 0) {
                this.add(postion, "#" + memo);
            } else {
                tempString = this.get(postion) + "";
                if ("#".equals(tempString.substring(0, 1)))// 判断截取的值
                    this.set(postion, "#" + memo);
                else {
                    this.add(postion + 1, "#" + memo);
                }
            }
        }
    }

    public void setTitle(String title) {// 设置注释内容
        String tmp= this.get(0) + " ";
        if (tmp == null || tmp.length() == 0)
            tmp = "";
        else {
            tmp = tmp.substring(0, 1);
        }
        if ("#".equals(tmp))
            this.set(0, "#" + title);
        else {
            this.add(0, "");
            this.add(0, "#" + title);
        }
    }

    public String getProperties(String key) throws UnsupportedEncodingException {
        return getProperties(key, "");
    }

    public String getProperties(String key, String defaultStr)
            throws UnsupportedEncodingException {
        String temp, resultString;
        for (int i = 0; i < size(); i++) {
            temp = get(i) + "";
            temp = new String(temp.getBytes("iso8859_1"), code);
            if (temp.indexOf(key) == 0) {
                resultString = temp.substring(key.length() + 1);
                return resultString;
            }

        }
        return defaultStr;
    }

    public void getValue() throws IOException {
        InputStream in = new BufferedInputStream(new FileInputStream(
                "/proper.properties"));
        Properties p = new Properties();
        p.load(in);
        String s = (String) p.get("studentName");
        String name = new String(s.getBytes("iso8859_1"), "GBK");
        System.out.println("输出studentName的值：" + name);
        String aString = (String) p.get("room");
        String room = new String(aString.getBytes("iso8859_1"), "GBK");
        System.out.println("输出room的值：" + room);
    }
}

 setTitle（）总是报错，求解这个错误原因在哪里？错误如下：

Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 0, Size: 0
 at java.util.ArrayList.RangeCheck(ArrayList.java:547)
 at java.util.ArrayList.get(ArrayList.java:322)
 at MyProperties.setTitle(MyProperties.java:137)
 at MyProperties.main(MyProperties.java:21)