List＜String＞、List＜Integer＞转逗号分割的字符串

public static void main(String[] args) {
    List list1 = new ArrayList<>();
	list1.add("a");
	list1.add("b");
	list1.add("c");

	//转换 String.join(",",list1); 
	System.out.println(String.join(",",list1));
	//输出结果 a,b,c

	List list2 = new ArrayList<>();
	list2.add(0);
	list2.add(1);
	list2.add(2);
	
	//转换 Joiner.on(",").join(list2); 
	System.out.println(Joiner.on(",").join(list2));
	//输出结果 0,1,2
}