编写java程序，要求：实现数组arr中索引位置是2 的元素替换为“bb”,并将替换前数组中的元素和替换后数组中的元素全部输出。-Write a Java program, requirements: realize index position is 2 element in the array arr is replaced by "bb", and will replace the former and replace all of the elements in an array of the elements in an array output.