value of ArrayIndexOutOfBoundsException: 20 ?

What does the value indicated by the ArrayIndexOutOfBoundsException means ?

i.e. java.lang.ArrayIndexOutOfBoundsException: 20

what's 20 ?

thanks

You tried to access the array with an index of 20, however that index is not valid for the array. In other words, your array is size 20 or less.