如何将数组的元素连接成一个整数

Question

有一个数组说arr与元素

6,5,1,0,9

我想要一个整数

a=65109

和

b=90156

Answer 1

    StringBuilder builder = new StringBuilder();
    for(int i = 0;i<arr.length;i++){
        builder.append(arr[i]);
    }
    long a = Long.parseLong(builder.toString());
    long b = Long.parseLong(builder.reverse().toString());
    System.out.println(a);
    System.out.println(b);

Answer 2

int arr[] = {6,5,1,0,9};
int result = 0,reverse = 0;
for (int i = 0; i < arr.length; i++) {
    result= result*10 + arr[i];
    reverse = reverse*10+arr[arr.length-1-i];
}
System.out.println(result);//number 65109
System.out.println(reverse);//number 90156