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)