Line $1$: Integer$[]$ intArray $=\{1,2,3\}$;

Line $2$: int i $=$ intArray$[0]+$ intArray$[1]$;

Line $3$: int j $=$ i $+$ intArray$[2]$;

Line $4$: double d $=$ intArray$[0]$;

Line $4$ is OK$.$ An int value from intArray$[0]$ object is assigned to a double variable d$.$

It is OK to automatically convert an Integer object to an int value in Line $2.$

It is OK to mix an int value with an Integer object in an expression in Line $3.$

It is OK to assign $1,2,3$ to an array of Integer objects since JD