I need these programs an Java for a dome program

void set$($int idx, int val$)\{$

$//$ Set the element located at idx with the given value.

$//$ eg$)$ Suppose elements $=[10,5,20,14,30],$ set$(1,99)$ changes it to $[10,99,20,14,30]$

$//$ Do nothing if idx is invalid.

$\}$

void add$($int idx, int val$)\{$

$//$ Add the given element $($val$)$ at the given location $($idx$)$

$//$ Assume that the given index is valid

$//$ Send the existing element to the end.

$//$ eg$)$ Suppose elements $=[10,5,20,14].$ add$(1,99)$ will change it to $[10,99,20,14,5]$

$//$ Make sure there are enough space for the new element.

$\}$

void add$($int$[]$ valArray$)\{$

$//$ Add all the elements of the given array 'valArray' at the end of the array 'elements'.

$//$ Make sure there are enough empty space for the new array.

$//$ Calling enlarge$()$ once may not be enough. ensureCapacity will be more useful.

$\}$

Integer max$()\{$

$//$ Return the maxinum value among the existing elements.

$//$ Return null if empty

return null; $//$ This is here to avoid syntax error. Change if needed

$\}$

int$[]$ copy$($int start, int end$)\{$

$//$ Return a new copy of the array between index 'start' and 'end' inclusive.

$//$ eg$)$ Suppose elements $=[10,5,20,14,30].$ get$(1,3)$ returns a new array $[5,20,14]$

$//$ Assume that both index start and end are valid.

$//$ If start $>$ end, then return the elements in reverse order.

$//$ eg$)$ Suppose elements $=[10,5,20,14,30].$ get$(3,1)$ returns a new array $[14,20,5]$

return null; $//$ This is here to avoid syntax error. Change if needed

$\}$