Java8语法糖List＜Integer＞，List＜String＞，List＜Long＞，String之间互转

public class Test {
    public static void main(String[] args) {
        List<Integer> integerList = new ArrayList<>();
        integerList.add(1);
        integerList.add(2);
        integerList.add(3);
        // List<Integer> 转为 List<String>
        List<String> stringList = integerList.stream().map(String::valueOf).collect(Collectors.toList());
        System.out.println("List<Integer> 转为 List<String>=====>" + stringList);
 
        //List<String> 转为 String 以逗号分隔
        String str = String.join(",", stringList);
        System.out.println("List<String> 转为 String 以逗号分隔====>" + str);
 
        //List<String> 转为 List<Integer>
        List<Integer> integerList1 = stringList.stream().map(Integer::valueOf).collect(Collectors.toList());
        System.out.println("List<String> 转为 List<Integer>====>" + integerList1);

        //List<String>转List<Long>
        List<Long> longList = stringList.stream().map(s -> Long.parseLong(s.trim())).collect(Collectors.toList());
        System.out.println("List<String> 转为 List<Long>====>" + longList);
    }
}