哪位大神帮我处理一下这个错啊，再下新手

Question

public class SeboResult {
public static void main(String[] args) {
String sebo = SeboResult.getSebo();
System.out.println(sebo);

}
public static String getSebo() {
    //红波  蓝波 绿波
    List<String> data = new ArrayList<>();
    data.add("红波");
    data.add("蓝波");
    data.add("绿波");
    int count = (int) (Math.random() * data.size());
    System.out.println("============"+count);
    //结果
    StringBuilder result = new StringBuilder();
    //获取随机索引
    //set去重复
    Set<Integer> set = new HashSet<>();
    for (int i=0;i<count;i++){
        int index = (int) (Math.random() * data.size());
        int size = set.size();
        set.add(index);
        //判断重复
        if(set.size() == size) {
            i--;
            continue;
        }
    }
    //5.去除默认逗号
    if(',' == result.charAt(result.length()-1))
            result = result.deleteCharAt(result.length()-1);
    // System.out.println(result);
    return  result.toString();
}

}
//这段代码报错：
Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: -1
at java.lang.AbstractStringBuilder.charAt(AbstractStringBuilder.java:237)
at java.lang.StringBuilder.charAt(StringBuilder.java:76)
at SeboResult.getSebo(SeboResult.java:39)
at SeboResult.main(SeboResult.java:11)

Answer 1

兄弟？将StringBuilder result = new StringBuilder();改为StringBuilder result = new StringBuilder("");