beanshell遍历字段值后如何将其拼接成数组，

如用使用beanshell将接口返回的title字段全部提取出来，并作为下一接口入参数？
{
"store": {
"book": [
{
"category": "reference",
"author": "Nigel Rees",
"title": "Sayings of the Century",
"price": 8.95
},
{
"category": "fiction",
"author": "Evelyn Waugh",
"title": "Sword of Honour",
"price": 12.99
},
{
"category": "fiction",
"author": "Herman Melville",
"title": "Moby Dick",
"isbn": "0-553-21311-3",
"price": 8.99
},
{
"category": "fiction",
"author": "J. R. R. Tolkien",
"title": "The Lord of the Rings",
"isbn": "0-395-19395-8",
"price": 22.99
}
],
"bicycle": {
"color": "red",
"price": 19.95
}
},
"expensive": 10
}

期望结果title_list["Sayings of the Century","Sword of Honour","Moby Dick","The Lord of the Rings"]

String str ="";
//title_matchNr为返回元素的数量，这里用于控制循环的次数
for(i=1;i<${title_matchNr}+1;i++){
String title = vars.get("title_"+i);
log.info(""+i+":"+title);
str += title +",";
}
str = str.substring(0,str.length()-1);
log.info("str:"+str);
vars.put("title_list",str);

List 的那个Stream 了解一下