public class SB {
    public static void main(String[] args) {
        StringBuilder sb = new StringBuilder();
        sb.append("Hello").append("Word").append("Java");  //链式编程，返回的是对象本身所以可以继续调方法
        System.out.println(sb);                              //append 方法 和    reverse 方法

        System.out.println(sb.reverse());          //反转字符串方法 reverse

        sb.append("Java");
        String s = sb.toString();                //StringBuilder 转为 String         通过toString方法
        System.out.println(s);

        String s1 = "Hello ";
        StringBuilder sb1 = new StringBuilder(s1);     //String 转为 StringBuilder  通过构造方法
        System.out.println(sb1);


        int[] array = {1, 2, 3};
        String result = PJ(array);         //调用拼接字符串方法
        System.out.println(result);


        Scanner scanner = new Scanner(System.in);
        String line = scanner.nextLine();
        String result1 = reverse(line);
        System.out.println(result1);
    }

    public static String PJ(int[] arr){                    //使用StringBuilder拼接字符串
        StringBuilder sb = new StringBuilder();
        sb.append("[");
        for (int i = 0; i < arr.length; i++) {
            if (i == arr.length-1){
                sb.append(arr[i]);
            }else {
                sb.append(arr[i]+",");
            }
        }
        sb.append("]");
        String s = sb.toString();
        return s;
    }
    public static String reverse(String s){            //使用StringBuilder反转字符串
//        StringBuilder ss = new StringBuilder(s);
//        ss.reverse();
//        String j = ss.toString();
//        return j;

        return new StringBuilder().reverse().toString();
    }
}