编辑代码

class Main {
	public static void main(String[] args) {
        System.out.println("--- 字符串 String ---");
        String s1 = "hello world";
        char c = s1.charAt(1);
        System.out.println("s1.charAt(1): " + s1.charAt(1));

        char[] chars = s1.toCharArray();
        chars[1] = 'a';
        String s2 = new String(chars);
        System.out.println("s2: "+s2);
		System.out.println("\n");

        System.out.println("--- 动态数组 ArrayList---");
        ArrayList<String> strings = new ArrayList<>();
        

	}
}