Bubble Sort Java? Using -1 after array.length

Hello

I am learning java and I am practising the bubble sort. I understand everything except.....

Could someone please explain the reason for using the -1 value after // numbers.length-1 in the 2nd for loop?

//more code here

for(int i=1; i<numbers.length; i++){

for(int j = 0; j < numbers.length-1; j++)

//more code here