JAVA 基础类型转换

一.数组、List

1. String[]  转  int[]

String menus_ = "1,2,3,4,5";
String[] sarr = menus_.split(",");
int[] menuIdArrs = Arrays.stream(sarr).mapToInt(Integer::parseInt).toArray();

 2.List 转 数组

ArrayList<String> list=new ArrayList<String>();
String[] strings = new String[list.size()];
list.toArray(strings);

3.String[] 转 List

String[] s = {"a","b","c"};
List list = Arrays.asList(s);

 4.List<String> 转 String

List<String> strList = [1, 2, 3];
String str = String.join(",",strList );

 5.String 转 List<Integer>

String str  = "1,2,3"
List<String> isStr =Arrays.asList(str.split(","));
List<Integer> isInt = new ArrayList<>();
CollectionUtils.collect(isStr, new Transformer() {
     @Override
     public Object transform(Object obj) {
        return Integer.valueOf(obj.toString());
     }},isInt);